#help-39

1 messages · Page 192 of 1

rancid steppe
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my answer sheet confirms it as x(a-b)(1+x) but it's the same tho right? ab=ba

warm copper
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yea

rancid steppe
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ty

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.close

pearl pondBOT
#
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rancid steppe
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$x^2(a-1) -9a + 9$

jolly parrotBOT
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Simon James B

rancid steppe
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to factor out 9 as a common factor do we consider the - ?

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so it would be $x^2(a-1) -9(a -1)$ but i confuse when we use there signs and when we have left 1

jolly parrotBOT
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Simon James B

rancid steppe
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how to we fector out from here

warm copper
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and when we have left 1
I'm confused what you mean by this part

rancid steppe
#

like we get a-1

warm copper
warm copper
pearl pondBOT
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mighty meteor
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this is a tuff one. I need your help, math nerds!

iron stream
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Bro

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Have you tried calculating A²

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I feel like you will get it Idempotent

mighty meteor
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imma be honest with you bro, i didnt even try to solve it ye

iron stream
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Do yk how to write matrix in wolfram ?

mighty meteor
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i just have a friend who said its hard

mighty meteor
iron stream
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Ok wait

mighty meteor
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i think ive seen this type of exercises before

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hold on

fringe raft
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can you diagonalize the matrix?

mighty meteor
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what is that even supposed to mean

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,,diagonalize,,

jolly parrotBOT
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Gustavo

fringe raft
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find S, so that S^-1 A S is a diagonal matrix

mighty meteor
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aaaah, its that formula

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yea idk how to use it

iron stream
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Finding A² and A³ would have led you to the conclusion

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That the diagonal elements aren't changing

mighty meteor
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wawawiwa

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thank you a lot Mr. Xor

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you always solve my problems

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ight bye

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.close

pearl pondBOT
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mighty meteor
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.reopen

pearl pondBOT
#

mighty meteor
mighty meteor
iron stream
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WTH wolfram gave us the wrong output

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No worries

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But

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You will have to calculate A² now

mighty meteor
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sure

iron stream
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And A³ too, so we find a sequence

mighty meteor
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sure ill do that

iron stream
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Did it ?

mighty meteor
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yea

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one sec

iron stream
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Ok

mighty meteor
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im gonna send it

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here

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i wrote them again for u

iron stream
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So 1st element doesn't change

mighty meteor
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looks like it

iron stream
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Second 1,10,28
Third 1,-8,-26

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So you see the pattern

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Yeahh

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1,1+9,10+9*2

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And 1,1-9,-8-9×2

mighty meteor
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huh?

iron stream
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Yeah for 2nd and third element of the diagonal

mighty meteor
iron stream
iron stream
mighty meteor
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ah, i see, you were talking about the term in the middle for all 3

iron stream
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Yeah that's what we're concerned about

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Now can you guess the next term ?

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For second it is, 28 +9*3

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And for third it is -26 - 9*3

mighty meteor
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so the formula is 10+9*(n-1)(-1)^n

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that should be it

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or wait, maybe not

iron stream
mighty meteor
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scratch that

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its wrong

iron stream
mighty meteor
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oh god

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sure

iron stream
mighty meteor
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here

iron stream
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,calc 28+27

jolly parrotBOT
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Result:

55
iron stream
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So we're correct

mighty meteor
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oh shiiiiii

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ok but still

iron stream
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The difference is always constant between second and third term

mighty meteor
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how would you find the formula

iron stream
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But now the question says to find the absolute addition value

mighty meteor
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for A^59 i think

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yes thats the matrice

iron stream
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Yeahh

mighty meteor
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so we gotta figure it out in terms of the exponent

iron stream
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Now we will explicitly calculate our sequence

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u is second diagonal element

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u2 = 1+9

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Hey say something

mighty meteor
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im still here

iron stream
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You know GP formula ?

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(r^n -1)/(n-1)

mighty meteor
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i forgot it

mighty meteor
iron stream
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a = 1 here

mighty meteor
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mhm

iron stream
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And we know the third element

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Is just 2 less than the second

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No need to separately compute it

mighty meteor
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hmm okie

iron stream
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,calc (9^59 - 1)/8

jolly parrotBOT
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Result:

2.49584763877e+55
mighty meteor
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wait, the third term is 55 right?

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so that wouldnt be it

iron stream
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u1 = A¹

mighty meteor
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ok so it should be 28 then

iron stream
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,calc 1+9+9^2+9^3

mighty meteor
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9^2 is 81

jolly parrotBOT
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Result:

820
mighty meteor
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which is already bigger than 28

iron stream
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Wait we had 3

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Wth

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We had 3

mighty meteor
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3 what?

iron stream
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Replace the 9s with 3 s wthhh

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Lemme retype

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Oh nah nah nah

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It's arithmetico-geometric progression

mighty meteor
iron stream
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Let me redo

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I'm on 3 hrs of sleep, i must sleep after this

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😭😭

mighty meteor
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sure

iron stream
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u1 = 1
u2 = 10 = 1 + 9
u3 = 28 = 1+ 9 + 2×9
u4 = 55 = 1+ 9 + 2×9 + 3*9

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So

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u_n = 1 + 9(1+2+...+(n-1))

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so u_n = 1 + 9×(n-1)(n)/2

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Now check this

mighty meteor
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thats 10621

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for n=59

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which is def not in the multiple choice

iron stream
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,calc 1+ 95859/2

jolly parrotBOT
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Result:

15400
mighty meteor
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right, my bad, still not there

iron stream
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,calc 15400*2 -2+1

jolly parrotBOT
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Result:

30799
iron stream
mighty meteor
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oh nvm

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i read it wrong

iron stream
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,calc 1+943/2

jolly parrotBOT
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Result:

55
iron stream
mighty meteor
iron stream
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And our 1st element is 1

mighty meteor
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so you calculated the third element when you did that?

iron stream
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So i just doubled the second

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And subtracted 2

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second + second -2 + 1
= 2×(second) -1

mighty meteor
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isnt it?

iron stream
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I'm still confused why wolfram gave that weird output!

iron stream
iron stream
mighty meteor
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so what does that mean

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addition to absolute values

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does it mean its in modulus?

iron stream
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Absolute values refers to the modulus value

mighty meteor
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oh wow

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thats really cool

iron stream
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2 +1

mighty meteor
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damn, thats right

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ok so the answer is a)

iron stream
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I will be going to bed ! Have a good day ! And sorry again ! I messed real bad !

mighty meteor
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fair

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ok bro

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goodnight

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mellow idol
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from the first recursion relation i got the 2nd result, is it correct?

mellow idol
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i was able to veirfdy it for 3 cases but wanna know if its correct

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i basically need to show that the first one diverges for all n, if the 2nd one holds true it trivialises that

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<@&286206848099549185>

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also is it fair to say that the harmonic series sum can excede 10^5 at some point

pearl pondBOT
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@mellow idol Has your question been resolved?

mellow idol
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<@&286206848099549185>

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if someone could gimme a yes or no that'd be great! ^^

hallow ice
hallow ice
mellow idol
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heady hearth
#

I gotta question on b, is there only one x intercept and if so is it 3,0?

frosty creek
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Almost. $(x+3)^2=0$ is true when $x+3=0$ or $x=-3$

jolly parrotBOT
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Calculustache

heady hearth
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Oh shoot i meant to put -3 thats my fault

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So there is only one x intercept right?

frosty creek
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Yeah. Because if you factor (x+3)^2 you have two (x+3) terms, meaning only one spot where it can equal zero

heady hearth
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Ok gimme a sec

bitter lodge
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Additional info in case you find it helpful: if the multiplicity of the root is a positive even number (in this case, 2 from (x + 3)^2), then the function comes to touch that root, then turns back around

heady hearth
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So your saying when its a positive in the parenthesis?

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Also what makes this top one have 2 different x intercepts?

frosty creek
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Graphically, you can think of the -4 moving the parabola down from where it barely touched the x axis to intersecting it at two points.

heady hearth
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So it move the whole graph down by -4 and where its at without the -4 is just at the point where moving it down causes it to go through the x intercepts twice?

frosty creek
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Yeah

heady hearth
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Ok and how would you be able to tell all of this without a graphing calculator

frosty creek
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You start with $(x+3)^2-4 =0$
$$(x+3)^2=4$$
$$(x+3)^2=\pm\sqrt{4}$$
Which has two answers and therefore two roots.

heady hearth
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Wait so this is a quadratic and so its already mostly solved but by completing the square?

jolly parrotBOT
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Calculustache

frosty creek
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Yes

heady hearth
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Ahhh ok this makes sense but the -4 is not moved yet

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So you move it now and then square root it and that gives plus or minus

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This is only because of this -4 but if you didnt have that you could do the thing with factoring?

frosty creek
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Yeah. Factoring or the quadratic formula.

heady hearth
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Ok but thats for the one without -4 but the one with negative four you have to, but why?

frosty creek
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Have to do what?

heady hearth
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Why not just do the thing with the equation that doesnt have -4 with the equation that does have -4?

frosty creek
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It is basically the same thing: move all constants to the right side and take the square root.

heady hearth
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Oh ok so both is the square root but for the one without the -4 its just the same making it have 1 x intercept

frosty creek
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Yeah.

heady hearth
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For this one first subtract the four?

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Then square root it but since its - make it i?

frosty creek
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Yes. It will be a complex number

heady hearth
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Because its a negative square root?

frosty creek
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Yeah

heady hearth
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Plus or minus 2i=x+3

frosty creek
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Yup

heady hearth
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Subtract 3 so its 3 plus or minus 2i=x ? Im doubting this as the numbers are in opposite placement from what i like

frosty creek
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Negative three plus or minus 2i

heady hearth
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Thats right thx for catching my mistake

frosty creek
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np

heady hearth
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So you really cant determine the roots?

frosty creek
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Not in the real numbers. That isn't to say they don't exist, but that you need a larger set of numbers to describe them.

heady hearth
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Yea so you cant really graph it?

frosty creek
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No.

heady hearth
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Alr

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This is confusing me its saying the sketch a graph of it and see if you can determine the roots but how do they expect us to graph it just by looking at it?

frosty creek
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Any parabola in the form $(x+a)^2$ will have a single x intercept, because it touches the x axis at one point (namely x=-a). So when you shift it up 4 units, it is no longer touching the x axis and will have no real roots

jolly parrotBOT
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Calculustache

heady hearth
frosty creek
heady hearth
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Ah ok

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So if it has lets say +8 on the outside and a plus in the parenthesis it wont hit the x axis? Because its raised by 8 and the plus on the inside makes it go up?

frosty creek
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Yeah

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Assuming the parabola "points" upwards

heady hearth
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Would you determine that by the plus or minus in the parenthesis?

frosty creek
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You would determine that based on whether or not it has a minus outside the parentheses.

heady hearth
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But that doesnt make sense what if its a negative on the our side but it foes down

frosty creek
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Yeah. So if it has a minus sign, then adding a positive number doesn't stop it from intersecting the x axis.

heady hearth
frosty creek
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If $x=-a$, then $(x+a)^2$ is the same thing as $(-a+a)^2=0$. No other value can make $(x-a)^2$ zero because no other value can make $x-a$ zero.

heady hearth
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This last part doesnt make sense i think its a typo it sats no ther

frosty creek
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If x=-a, then (x+a)² is the same thing as (-a+a)²=0. No other value can make (x-a)² zero because no other value can make x-a zero.

jolly parrotBOT
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Calculustache

frosty creek
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Alr I have to go.

heady hearth
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Ah ok this last part doesnt make sense to me tho

pearl pondBOT
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@heady hearth Has your question been resolved?

pearl pondBOT
#

@heady hearth Has your question been resolved?

heady hearth
#

@helper

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<@&286206848099549185>

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This is the question ignore all the work

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This is the work ive done

spiral pivot
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Interesting that the minimum is outside of the range of the two zeroes

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This kind of implies to me that it's perhaps something like an exponential times a quadratic or something of the sort perhaps?

heady hearth
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All i know is i must find a but i forgot how to and i dont wanna cheat and look at the answer

spiral pivot
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There is no a that will satisfy this requirement.

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If you're talking about ax^2 + bx + c

heady hearth
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No im pretty sure ot something that multiplies to everything to make it true

spiral pivot
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And I'm pretty sure there isn't

heady hearth
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The minimum or maximum is the vertex right?

spiral pivot
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Yes

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And the vertex must always lie between the zeroes

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But -8 isn't between 1 and -7

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So this isn't a quadratic

heady hearth
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So to get the vertex from the x intercepts you add the x intercepts and divode by two?

spiral pivot
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Yes, which would place it at -3

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Oh, is -8 the minimum y value?

heady hearth
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Wait

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Would i make it so something times the equation i have =-8?

spiral pivot
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f(-3) = -8 yeah

heady hearth
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Wait im confused

spiral pivot
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Ok you have a quadratic right?

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f(x) = a(x-r)(x-s)

heady hearth
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Yes

spiral pivot
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You know r and s are 1 and -7

heady hearth
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The second one isnt minus tho

spiral pivot
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So you have f(x) = a(x-1)(x+7)

heady hearth
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Yes

spiral pivot
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So we have f(-3) = -8

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So f(-3) = -8 = a(-3-1)(-3+7)

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Solve for a

heady hearth
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Wait could we just assume the f() is just y?

spiral pivot
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Yes, typically f(x) = y

heady hearth
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Ok wait lemme process this

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Wouldnt it be positive 3?

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Wait nvm

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I read it wrong

heady hearth
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@spiral pivot

spiral pivot
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I evaluated the function at -3

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By replacing the x with -3

heady hearth
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Hold on the x intercepts we have are 1 and 7 so we got (x-1) and (x+7)

spiral pivot
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Yes

heady hearth
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That vertex doesnt match the one it gives

spiral pivot
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The one what gives?

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b/2a ?

heady hearth
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No the vertex it gives -8

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We get -3 tho

spiral pivot
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Yup, that's why I started out confused as well

spiral pivot
heady hearth
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So we have to make the x-8 x+7 =8

spiral pivot
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The vertex is at (x, -8) not (-8, y) like I thought

heady hearth
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-8 mb

spiral pivot
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The vertex is at (x, -8)

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-8 is the y coordinate

heady hearth
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Correct

spiral pivot
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Not the x coordinate

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The x coordinate is where the vertex must be, which is -3

heady hearth
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So wouldnt it just be -8 is = what we multiply it by which will stand for a times the x-1 abd x+7?

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@spiral pivot

spiral pivot
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I explained, the vertex is at -3

heady hearth
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The one we got

spiral pivot
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This is independent of a

heady hearth
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What do you mean independent of a?

spiral pivot
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Doesn't matter what number a becomes, the vertex is decided by r and s

heady hearth
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This doesnt make sense can you change the x intercepts? Cause i dont thibk you can

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@spiral pivot

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Bro i need help pls

spiral pivot
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You can't change the x intercepts, which means that the x coordinate of the vertex is fully specified from the given information

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And it's -3

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A better question is do you know how to find the vertex?

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It's simply the average of r and s, the two roots

heady hearth
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Wait so we found the x but what it says about the vertex is the y?

spiral pivot
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Yes

heady hearth
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Wait i thibk i get it now lemme write it down and show you

spiral pivot
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Exactly

heady hearth
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Ok but i dont understand why would we weote it in this equation ?

spiral pivot
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Trying to solve for a

heady hearth
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Why though?

spiral pivot
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Need to know a to write the equation

heady hearth
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Why isnt x^2+6x-7

spiral pivot
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Because it's a times that

heady hearth
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Why though?

spiral pivot
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Because a(x-r)(x-s) is the formula for the quadratic

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But x^2 + 6x - 7 is just (x-r)(x-s)

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Going afk. Best of luck!

heady hearth
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Alr

spiral pivot
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Sorry I have to jet

heady hearth
#

Ah ok

heady hearth
#

What os the differences between a quadratic function and equation

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<@&286206848099549185>

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.close

pearl pondBOT
#
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spiral pivot
#

@heady hearth the difference between a function and an equation is the equation finds the roots of the function

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0 = ax^2 + bx + c

Vs

f(x) = ax^2 + bx + c

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Top is the equation, the bottom is the function

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But that being said, not everyone who writes math problems is careful, for your question I would write the function.

pearl pondBOT
#
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stoic imp
pearl pondBOT
plush sundial
#

what did u try

tranquil cobalt
#

just angle chasing

stoic imp
tranquil cobalt
#

yes

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and u know that triangle is isoceles

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cuz all the sides r equal

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those who know 💀 💀 💀

stoic imp
#

yipee

tranquil cobalt
#

yes i think

#

good boy

stoic imp
#

.solved

pearl pondBOT
#
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smoky mantle
pearl pondBOT
smoky mantle
#

I do not know what to do at all 😭

limpid lily
#

The maximums (a kind of extreme point) will occur at the endpoints or when the first derivative is zero.

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So, it might happen when x = -4 or x = 3.

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It might happen when (x^2 + 3) cos(x - 5) is zero.

smoky mantle
#

do I just plug in for -4 and -3?

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wait no

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I'm sorry, I'm usually not this stupid I swear

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I'm so tired from doing my other assignments that I can't even keep my eyes open long enough to try to understand the question

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It's due in a couple of hours and I haven't slept yet

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😭

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It's a struggle out here frfr

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I have like 4 more of these to do and another 5 questions for another section and atp I just want to get it over with 🙏

limpid lily
#

Have you done integrals or antiderivatives yet?

smoky mantle
#

I don't think I've done integrals yet no

limpid lily
#

Have you done antiderivatives?

smoky mantle
#

haven't done that either

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I got this assignment out of nowhere and it's based on completion

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but I can't complete it if I don't get it right wdoadja

limpid lily
#

OK, so let's look at the endpoints.

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x = -4.

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Let's say we have a graph of f(x).

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And let's say that x = -4 is a maximum.

smoky mantle
#

okay

limpid lily
#

What would be happening with the derivative?

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At x = -4?

smoky mantle
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I'm not sure

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oh

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do I just plug in for f'(-4)?

limpid lily
#

No.

smoky mantle
#

oh

limpid lily
#

The derivative is the slope of f.

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So, if f(-4) was a maximum, it would be going down as you go to the right.

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Because it's higher at the maximum than the stuff around it.

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Does that make sense?

smoky mantle
#

yes

rose robin
#

I don't think you can just plug in values
you need to take the integral then solve for the constant

limpid lily
#

So, the slope would be negative.

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Is f'(-4) (note f', not f) negative (or zero)?

smoky mantle
#

would it be 0?

limpid lily
#

It could be.

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But they give you the formula for f'(x), right?

smoky mantle
#

yes

limpid lily
#

Fill in -4 for x in that and see if it's negative or zero.

smoky mantle
#

(x^2+3)cos(x-5)

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-13*cos(-9)

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I got 11.844 pos

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what

limpid lily
#

It can't be -13.

smoky mantle
#

hold on

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I did something wrong

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it's 13cos(-9)

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I got a negative number

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-11.844**

plush sundial
#

for fining maxima or minima u shud equate f'(x) = 0 and find the possible values

smoky mantle
#

so equate (x^2+3)cos(x-5) = 0?

plush sundial
#

yes

smoky mantle
#

okay I'll try doing that

limpid lily
#

For example, y = x^2 in the interval [-5, 10] will have two maximums, both at the endpoints.

smoky mantle
#

welp thanks for trying to help but I honestly am not comprehending anything you're saying

#

like my brain is deep fried

limpid lily
#

You should sleep.

smoky mantle
#

I'll just accept the loss and go to sleep 🫡

#

good night 😭

limpid lily
#

You too.

smoky mantle
#

.close

pearl pondBOT
#
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pearl pondBOT
#
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pulsar berry
pearl pondBOT
pulsar berry
#

Find the sum of the series

#

I have no idea how to approach this

gleaming musk
#

is there no context to this>

#

seems uncharacteristic of questions to just hae 4 variables undefined without any purpose

#

but for starters there are some rearranging u could do to start of

#

the denominator could be rewritten as something much cleaner, and same for the other term (u^n/2)/z^{n/3}

pearl pondBOT
#

@pulsar berry Has your question been resolved?

pulsar berry
#

Yeah that’s what is not clear to me

#

It can be written like this too

#

But what is not clear to me is how to deal with x, y, z, and u

gleaming musk
#

nothing immediately jumps at me tbh

pearl pondBOT
#
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gleaming musk
#

.reopen

pearl pondBOT
#

#

@pulsar berry Has your question been resolved?

pulsar berry
#

It feels impossible

pulsar berry
#

<@&286206848099549185>

stable dune
#

Man this looks like some special functions type of thing

#

I dont know many of those off the top of my head tho

#

Wouldn't we want x-y

#

The sum on the bottom is raised to the n for each variable

hot canyon
#

Oh shiii

#

Then it's a issue (@_@;)

stable dune
#

Yeah uhh

#

This seems real tough

#

Ramanujan-like even

hot canyon
#

T-T where's the context for the question

hearty dew
#

I dont think you can get a specific sum of the series

hot canyon
stable dune
hearty dew
#

but I can't think of any

stable dune
#

Like u gotta realize that one of these is a representation of the digamma or smth crazy

hearty dew
#

I kinda agree with you on that one

pulsar berry
#

Is from analysis 2 class

hearty dew
stable dune
#

It's like super rigorous multivariable calculus

hearty dew
#

Oh my

#

Im going to pretend I didnt see this channel

pearl pondBOT
#

@pulsar berry Has your question been resolved?

#
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#
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hearty condor
#

Let f be a function that its domain includes a neighborhood of x0, U.
The limit of f(x) as x approaches x0 exists.
Does a neighborhood of x0 exist, such that every t in that neighborhood, the limit of f(x) as x approaches t exists?

hearty condor
autumn trellis
#

okay, so it is wrong

hearty condor
#

Really?

autumn trellis
#

i think you are restricting the images in your mind to continuous functions

hearty condor
#

I tried checking f(x)={x} or floot function

autumn trellis
#

if you remove this assumption you may come up with counterexamples

hearty condor
#

Floot

#

Floor

autumn trellis
#

thats continuous almost everywhere

hearty condor
#

Well what's a function that's continous not almost everyehere

autumn trellis
#

well, think of something LIKE $f(x) = 1$ when $x$ is rational and $f(x) = 0$ when $x$ is irrational

jolly parrotBOT
#

4573r01d|)d357r0y3r 45²

hearty condor
#

The D function?

tropic saddle
#

you can find a function thats continuous almost everywhere and for which the claim is still wrong

autumn trellis
tropic saddle
#

real analysis has some quite cursed counterexamples

stable dune
#

Wouldn't dirac delta be a counterexample

hearty condor
#

Yeah but how do we add a limit to it. 😭 if we make a neighborhood around a specific point then we can use that neighborhood as the example

autumn trellis
#

okay what if you made the f(x) = 1 part to f(x) = x...

hearty condor
#

Hmmm

#

Then 0 would have a limit

hearty condor
cinder thistle
autumn trellis
autumn trellis
hearty condor
#

Yeah he also talked about that 😭

cinder thistle
hearty condor
tropic saddle
#

and if you are up for more fun, consider the function $$f(x) = \begin{cases} \frac1q & x=\frac p q, \gcd(p,q)=1 \ 0 & \text{ else}. \end{cases}$$ and think about where that function is continuous

jolly parrotBOT
#

Denascite

hearty condor
#

I dont think thats fun 💔

tropic saddle
#

then ignore it

autumn trellis
#

||this is a classic, continuous at all irrationals/||

hearty condor
#

What is gcd again?

tropic saddle
#

greatest common divisor

#

aka, p/q is fully reduced

hearty condor
#

Ah

autumn trellis
#

well anyways i think you have a few counterexamples now

hearty condor
#

Yes, thanks a lot

#

.close

pearl pondBOT
#
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stiff mauve
#

can someone help me with 1a

pearl pondBOT
gleaming musk
#

what have u done so far

stiff mauve
#

this is supposed to be the answer

#

but

#

this is what i have

gleaming musk
#

ok before anything

#

im not saying it was the fualt here but just be careful since ur 4s do look like a

stiff mauve
#

true i get what u mean

gleaming musk
#

do u have more working out or did u just skip a bunch of stpes

#

it should reasoning ur 2nd column be all 0 since

#

the first entry is a multiple of 2 of the 2nd entry

stiff mauve
#

i mean i divided the 2nd row by two

#

so we have 0, a-2, a, a-2

#

and then

#

Row 3 - (new) Row 2 would become my new row 3

#

owww

stiff mauve
#

forgot to do the 4th (b) column

#

im still stuck

gleaming musk
#

ur row 3 column 4 is still wrong

#

before u did ur subtraction

#

ur row 3 should be
0 a-2 a^2 | 2a-3 right?

#

and ur row 2: 0 a-2 a| a-2

stiff mauve
#

yes @gleaming musk

gleaming musk
#

u should have an a left in ur column 4

gleaming musk
#

2a-3-(a-2)

#

a-1

stiff mauve
#

right

gleaming musk
stiff mauve
#

ye i changed it now on my paper

#

how can i continue after this?

gleaming musk
#

i mean its echelon form already tbh

#

even tho u can simplify it

stiff mauve
#

shouldnt echelon be 1 1 1 on diagonals

gleaming musk
#

not always?

stiff mauve
#

its either 1

#

or 0

gleaming musk
#

no?

stiff mauve
#

right?

#

why not

gleaming musk
#

the quesiton doesn't specific reduced

#

it just says echelon

#

ok let say for the sake of quesiton u want to reduce this further

#

ur 2nd row should be pretty obvious

#

0 a-2 a | a-2

stiff mauve
#

divide evrtyhing by a-2 right

gleaming musk
#

nope

#

what is that row saying

stiff mauve
#

x2 = 1

#

x3 = 0

gleaming musk
#

oh wait sorry im looking at the wrong thing

#

row 3 not row 2

#

0 0 a^2-a | a-1

stiff mauve
#

x3 = 1/a

gleaming musk
#

=?

stiff mauve
#

1/a x (a^2-a) = a - 1

gleaming musk
#

wait

#

hold up

#

sorry let me backtrack

gleaming musk
#

im pretty sure it is in echelon form right here

#

idh paper on me so maybe i have it wrong in my mind

#

can u send a photo of what u have written down back here

stiff mauve
#

@gleaming musk

gleaming musk
#

ok

#

can we reduce the third row a little bit more

#

actually dont

gleaming musk
#

its in row echelon form

#

1a) is only asking for echelon form

#

i think u have the wrong definition of echelon

stiff mauve
#

why are they distingqushing cases for a = 2 then

gleaming musk
#

u end up with a column of 0s

stiff mauve
#

does echelon basically mean there is a pivot in each row/column

gleaming musk
#

and they are just showing that it is still in echelon form

gleaming musk
stiff mauve
#

ahh and for a = 2

gleaming musk
#

dont confuse it with reduced

stiff mauve
#

there isnt a pivot in row 3?

acoustic pagoda
#

bro is on the flow of reduction lol

gleaming musk
stiff mauve
#

so for a = 2

#

2a - 4 is = 0

#

so the first pivot in the 2nd row is in column 3

gleaming musk
#

oh thats what u meant

#

yeah sure

#

its just specificy when the variable is free and u end up with that situation

stiff mauve
#

and so there is no pivot in the third row roght

gleaming musk
#

yes

#

and then u have to manipulate it into echelon form

#

also before

#

dont confuse reduced with just normal echelon form

stiff mauve
#

yes

#

ty

pearl pondBOT
#

@stiff mauve Has your question been resolved?

#
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ebon burrow
pearl pondBOT
#
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
ebon burrow
#

1

tropic saddle
#

have you just tried filling in some numbers in a 3x3 grid and seeing what the dog and cat would write?

ebon burrow
#

Although I know of the 3 x 3 grid

ebon burrow
#

9 6 1
2 5 8
3 4 7

#

@tropic saddle

cinder thistle
#

the cat wont get 84

tropic saddle
#

what do the cat and dog write?

ebon burrow
#

The products of a row and columns as sets

#

Which must be equal (unordered sets)

#

@tropic saddle

tropic saddle
#

not sure why you are bringing sets into this

#

also all sets are unordered

#

what actual numbers do the cat and dog write for your grid

ebon burrow
#

What?

tropic saddle
#

the cat writes down three explicit numbers

#

which ones

ebon burrow
cinder thistle
#

oh

#

the the dog wont get 84

ebon burrow
#

Ok

cinder thistle
#

but the cat gets 84

tropic saddle
#

but what are those products

#

I am asking you to calculate them

ebon burrow
#

Oh

#

But depends on the grid

tropic saddle
#

well yes

#

but you gave a grid

#

which you claimed worked

ebon burrow
#

It doesnt

#

I was wrong

tropic saddle
#

ok then try a different grid

#

see if you can get one to work

#

this is expected to take some time experimenting

ebon burrow
#

Let's see

#

@tropic saddle

#

9 6 1
3 5 8
2 4 7

#

Dog = {54, 120, 56}

#

Cat = {54,120,56}

#

@cinder thistle

cinder thistle
#

yes this works

ebon burrow
#

@cinder thistle what to do next

cinder thistle
#

notice 5 and 7 are completely unshared

#

try showing 5 is impossible

ebon burrow
#

How?

cinder thistle
#

i mean

#

that a 5x5 grid is impossible

ebon burrow
#

@cinder thistle

#

@tropic saddle

tropic saddle
#

experiment

ebon burrow
#

But 5! Many combinations are too much

#

120 (many of them are equivalent)

tropic saddle
#

there are a lot more

#

but thats not the point

#

just try out a few

#

see what fails

#

pay attention to primes

ebon burrow
#

Ok trying

#

Doesn't work for 5 x 5

tropic saddle
#

why

ebon burrow
#

Idk

#

I wrote a comp program to print all such grids

#

Works for 3

#

(which i write)

tropic saddle
#

sigh

ebon burrow
#

But doesn't work for 5x5

tropic saddle
#

do it by hand

ebon burrow
#

I tell you man

tropic saddle
#

yes but you dont know why

ebon burrow
#

Also, it is kinda urgent

tropic saddle
#

if you had done it by hand you would know why

ebon burrow
#

I have been stumbling on it for like 5 days

#

Tomorrow is the submission

tropic saddle
#

ok unlucky for you

ebon burrow
tropic saddle
#

but this is an exercise which requires time spent by you

#

trying out stuff

ebon burrow
#

I could do 6/8 problems

#

But can't do this and one more

ebon burrow
#

I did IT!

tropic saddle
#

why not

pearl pondBOT
#

@ebon burrow Has your question been resolved?

pearl pondBOT
#
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regal herald
#

<@&268886789983436800>

iron stream
#

abcdefghijklmnopqrstuvwxyz

pearl pondBOT
#
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prime bramble
pearl pondBOT
#
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exotic gale
#

Can someone please help me with this question

exotic gale
#

At first, I tried to solve it using brute force

#

But I think there should be a smarter way to solve it

#

<@&286206848099549185>

#

<@&286206848099549185>

cinder thistle
#

Mod 10

pearl pondBOT
# exotic gale <@&286206848099549185>

Please only use the <@&286206848099549185> ping once if your question has not been answered for 15 minutes. Please do not ping or DM individual users about your question.

pearl pondBOT
# exotic gale <@&286206848099549185>

Please only use the <@&286206848099549185> ping once if your question has not been answered for 15 minutes. Please do not ping or DM individual users about your question.

exotic gale
#

sorry for spamming the command my pc was glitchy

exotic gale
#

Can you please elaborate

wet swallow
#

All I see is the unit digits repeat

cinder thistle
#

Unit digits

#

Are the remainders when divided by 10

exotic gale
#

oh okay

iron stream
#

3+5+7+9+1 = 25

#

25*2 = 50

#

So 10 terms of course!

wet swallow
#

@exotic gale

exotic gale
#

why'd you tell me the answer

#

but okay

#

thanks nevertheless

#

.close

pearl pondBOT
#
Channel closed

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pearl pondBOT
# iron stream So 10 terms of course!

As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.

#
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stoic imp
#

In this problem, $a$ and $b$ are positive integers.

When $a$ is written in base $9$, its last digit is $5$.

When $b$ is written in base $6$, its last two digits are $53$.

When $a-b$ is written in base $3$, what are its last two digits? Assume $a-b$ is positive.

jolly parrotBOT
#

938c2cc0dcc05f2b68c4287040cfcf71

autumn fossil
#

this could probably be converted to a modulo problem

#

idk if there's a simpler way, but the modulo one is quite short

autumn fossil
stoic imp
#

the remainder after the division, no?

autumn fossil
#

so how could you rephrase the first statement about a in terms of modulo?

stoic imp
#

a = x*9^n + y *9^n-1 + ... + 9^0 * 5

#

idk

autumn fossil
autumn fossil
#

would you be able to convert a to base 3?

#

how many digits of the base-3 expansion would we get to know?

stoic imp
#

a = x * 3^2n + y * 3^2n-2 + ... + 3^0 * 5

stoic imp
#

at the very least one

autumn fossil
stoic imp
#

5 in base 9

#

,w 5 in base 9 to base 3

jolly parrotBOT
autumn fossil
#

5 = 1 * 3^1 + 2 * 3^0

#

thats the logic behind the 12

stoic imp
#

5 = 9^0 * 5 = 5

autumn fossil
#

yeah, that's in base 9

autumn fossil
#

like that

stoic imp
#

a = x * 3^2n + y * 3^2n-2 + ... + 3^1 *1 + 3^0 * 2

autumn fossil
#

a = ....12 base 3

#

Do we need any other digits though?

#

We have 2 digits of a in base 3

#

and in the end, we want 2 digits of a - b also in base 3

#

so knowing 2 digits of a should suffice

#

so we can now move onto b

#

did you understand how a was done?

autumn fossil
stoic imp
#

b = ... + 6^1 * 5 + 6^0 * 3

autumn fossil
#

try rewriting it in base 3 now

stoic imp
#

5 = 3^1 * 1 + 3^0 * 2

#

ahh is so confusing

#

3 = 1* 3^1

#

b = ... + (1+1)*3^1 + 2 * 3^0

autumn fossil
#

let me check...

autumn fossil
autumn fossil
#

and all we need is to rewrite it in form ... + sth * 3^1 + sth * 3^0 while preserving equality

#

you could even just write it in your favorite familiar number system, base 10 and then convert it manually to base 3

#

so like 6 * 5 + 3 = 33

#

and then write that in base 3

#

33 = 27 + 6 = 3^3 + 6 = 3^3 + 2 * 3 = 3^3 + 2 * 3^1

#

oh wait

#

i really just wrote 6 = 3 + 2 *facepalm*

pearl pondBOT
#

@stoic imp Has your question been resolved?

stoic imp
#

33 = (3^3) + 2(3^1)

autumn fossil
#

yep

#

and taking the last 2 digits of that, what do we get?

#

(in base 3)

stoic imp
#

12

autumn fossil
#

you sure?

stoic imp
#

,w 33 in base 3

autumn fossil
#

there are some missing 0's basically

#

namely 0 * 3^2, 0 * 3^0

stoic imp
#

1(3^3) + 0(3^2)+ 2(3^1) + 0(3^0) = (3^3) + 2(3^1)

autumn fossil
#

almost

autumn fossil
#

1(3^3) + 0(3^2)+ 2(3^1) + 0(3^0)

#

so it would be this

#

now the last 2 digits of that are 20

#

in base 3

#

so now the last part is subtracting a and b in base 3

stoic imp
#

1(3^3) + 0(3^2)+ 2(3^1) + 0(3^0) = (3^3) + 2(3^1)

autumn fossil
#

. 12
- 20

#

and we need to do that subtraction base 3

stoic imp
#

a = ... + 1(3^1) + 2(3^0)
b = ... + 1(3^3) + 0(3^2)+ 2(3^1) + 0(3^0)

autumn fossil
#

okay, this'd work too

#

b = ... 2(3^1) + 0(3^0)

#

btw we could also write b like this, becasue we only need 2 digits

#

and now you just need to subtract them

autumn fossil
stoic imp
#

a = ... + 0(3^3) + 0(3^2) + 1(3^1) + 2(3^0)
b = ... + 1(3^3) + 0(3^2)+ 2(3^1) + 0(3^0)

autumn fossil
#

remember that we only need the last 2 digits

#

we only need the 3^1 and 3^0 terms

stoic imp
#

a = ... + 1(3^1) + 2(3^0)
b = ... + 2(3^1) + 0(3^0)

autumn fossil
#

and now subtract them

stoic imp
#

a-b = ... + (1-2)(3^1) + (2-0)(3^0)

#

but is negative number

autumn fossil
#

yeah

#

how do we solve this issue in decimal system?

stoic imp
#

-1x3 + 2

autumn fossil
#

If you were to subtract e.g.
100 + 10 + 4
40 + 3

#

so
114
-43

#

1 - 4 is also negative

#

how do we solve that?

autumn fossil
#

do you know the subtraction algorithm?

#

the one where you place the numbers under each other and then compute the difference digit by digit

#

it looks like this when on paper

#

do you know that?

stoic imp
#

I got lost

#

I understand tiling here

a-b = ... + (1-2)(3^1) + (2-0)(3^0)

stoic imp
autumn fossil
#

and we ran into the issue that 1 - 2 is negative

#

what im trying to point out is that the same issue happens when we do subtraction in base 10

autumn fossil
#

e.g. when we try to subtract
114
-43

we run into the issue of 1 - 4 being negative

#

when computing the tens digit

stoic imp
#

why 114 43

#

I got lost again tbh

autumn fossil
#

e.g. means for example

autumn fossil
stoic imp
autumn fossil
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how did you get 11?

stoic imp
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idk how to explain it is how math works

autumn fossil
#

you basically added 10 to the 1

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and 10 is the base we're working in

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and exactly the same method works for base 3

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we can just add 3

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so the 1 - 2 would turn into 4 - 2

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a-b = ... + (1-2)(3^1) + (2-0)(3^0) = ... + (4-2)(3^1) + (2-0)(3^0)

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we are basically adding 3*3^1

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and what happens algebraically is that it becomes 3^2

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so it moves behind the dots and it's no longer our issue

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since we only care about the last 2 digits

stoic imp
#

okay i get it

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so?

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a-b = ... + 2x3+ 2

autumn fossil
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yepp

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so the last 2 digits are...?

stoic imp
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2, 2

autumn fossil
#

yeah

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22

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you can also subtract the numbers directly using the same algorithm as in base 10, except replace 10 with 3

stoic imp
autumn fossil
#

so like
12
-20
the last digit is 2 - 0, we carry nothing. Then we have 1 - 2 so we add 3 to get 4 - 2 which is 2 and we carry 3, but that's no longer our issue since we only cared about last 2 digits

autumn fossil
#

a = 5 (mod 9) is equivalent to 5 being last digit of a in base 9

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similarly, b = 33 (mod 36)

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and so b = 6 (mod 9)

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a - b = 5 - 6 = -1 = 8 (mod 9)

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and 8 = 2 * 3 + 2 which is 22 base 3

pearl pondBOT
#

@stoic imp Has your question been resolved?

pearl pondBOT
#
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#
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orchid cobalt
pearl pondBOT
orchid cobalt
#

i got 20.29

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and i did (8.2)/tan68

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but the answer is 3.31!

plush bramble
#

,calc 8.2/tan(68 deg)

jolly parrotBOT
#

Result:

3.3130150518483
orchid cobalt
#

oh

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OH WAS I SUPPOSED TO USE THE INVERSE ON THE CALC?

warm current
#

what

orchid cobalt
#

ok wait that didnt work

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mb

orchid cobalt
warm current
#

what is tan(45) in your calc

orchid cobalt
#

1

plush bramble
#

What's tan(68) on your calc

orchid cobalt
#

guys im still getting 20.29

orchid cobalt
#

rounded

plush bramble
#

,calc tan(68 deg)

jolly parrotBOT
#

Result:

2.4750868534163
plush bramble
#

Right

orchid cobalt
#

oh wait, i forgot to divide.

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wait lemme try dividing

plush bramble
orchid cobalt
#

omg i got it!!

plush bramble
#

,calc 8.2tan(68 deg)

jolly parrotBOT
#

Result:

20.295712198014
orchid cobalt
#

wait what would the tan-1 be for then?

plush bramble
#

I see

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That's inverse tangent function

orchid cobalt
plush bramble
#

Also called arctan

orchid cobalt
plush bramble
#

No you would not

orchid cobalt
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alright thank you so much! ❤️

limpid lily
#

The -1 doesn't mean reciprocal. It means undo this function. So, like if you have tan(50 degrees) and you run tan^-1 on it, you get back 50, loosely.

#

,calc tan(50 deg)

jolly parrotBOT
#

Result:

1.1917535925942
limpid lily
#

,calc atan(1.1917535925942) * 180 / pi

jolly parrotBOT
#

Result:

50
orchid cobalt
#

so itls like f^-1!!

limpid lily
#

Right.

orchid cobalt
#

thank you so much!!

limpid lily
#

No problem.

orchid cobalt
#

.close

pearl pondBOT
#
Channel closed

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pearl pondBOT
#
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wheat remnant
#

Is this a valid approach and are these graphs correct?

wheat remnant
#

<@&286206848099549185>