#help-4

1 messages · Page 33 of 1

ivory valley
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Now you check when x+4>0 and x-4>0

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That means x>-4 and x>4

orchid thistle
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hold on [\f(x+4}{x-4} ≥ 0 ]

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ow it dosnt work

orchid thistle
rocky lotusBOT
orchid thistle
#

does ge mean greater equal to?

ivory valley
#

It's my custom preamble so it won't work on you

orchid thistle
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ow 😢

ivory valley
#

You have good examples how to draw x>-4 and x>4

orchid thistle
#

ts the thing i dont

ivory valley
#

You first draw a line

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Take the less value, here -4 and start to draw the line with integers starting from -4

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I will do the example with integers first

orchid thistle
ivory valley
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x>-4 would have {-3,-2,-1, ... , 4, 5, 6 ...}

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x>4 would start from 4 but excluding it so {5, 6, ...}

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Now you can see there are numbers that one list doesnt contain

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When we look for the intersection we look for all numbers that both lists contain

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The list x>-4 contains also the numbers in x>4, does that make sense?

orchid thistle
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yes somewhat

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x>-4 is like -4→+inf?

ivory valley
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Yes but without -4 because there is no equal sign

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This is where math ppl write (-4,+oo) instead of [-4,+oo)

orchid thistle
#

oo

ivory valley
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infinity

north walrus
#

orchid thistle
#

i meant to mean say smth like "ooh" xd

ivory valley
orchid thistle
#

So we put a close asymptote at -4? with like an arrow reaching to inf?

ivory valley
#

Drawing is much better because you would only have to figure where both "arrows" overlap

orchid thistle
#

ic

ivory valley
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The overlap happens when x>4

orchid thistle
#

So thats the answer i needed or is there something that i need as well?

ivory valley
#

Numbers in green are also im blue contained

ivory valley
#

The second is when the expression is 0

orchid thistle
ivory valley
#

So you check the numerator when that is 0

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The third case is when both the numerator and denominator are negative

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Because dividing a negative number by a negative number returns a positive number

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  1. x+4=0
  2. x+4<0 and x-4<0
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Try the 3. case by drawing

orchid thistle
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ill bookmark ts i have class ty for help

#

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solemn vortex
#

Guys I can’t understand the integrers

sharp whale
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bro is saying it with the hard r

solemn vortex
#

lol yes

wraith heart
solemn vortex
#

I don’t

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My bad I waste tour time

sharp whale
#

.close ok

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river shale
#

.reopen

vale dockBOT
#

river shale
solemn vortex
#

Like what is it used for

stiff flower
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counting usually

sharp whale
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the integers are 0, 1, -1, 2, -2, 3, -3, and so on

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theres a lot of uses for positive and negative whole numbers

solemn vortex
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Ok

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So it’s to count in specific order

river shale
sharp whale
solemn vortex
#

Ah now I understand

lavish mortar
sharp whale
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thats just a list of things, it doesnt mean a specific order

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I couldve listed them as ... -3, -2, -1, 0, 1, 2, 3, ...

solemn vortex
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Ok it will dépend

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Yea thanks

#

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orchid thistle
#

Hello, Rational Inequalities.
(2x/(x-4))≥1

orchid thistle
#

further discussion from my previous one

magic lynx
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two options to do this

#
  • simplify the right hand side as a mixed fraction
  • multiply both sides by x-4. this requires casework on whether x-4 is positive or negative
orchid thistle
orchid thistle
magic lynx
orchid thistle
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what does casework men

stiff lily
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considering what happens under certain conditions/assumptions

stark wedge
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and if we're being honest, also not recommended even here.

stiff lily
#

if you want the multiplication route, multiply by (x-4)^2,
and instead of annoying algebraic casework, you can use wavy method

magic lynx
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btw i meant simplify left hand side, not right hand side

orchid thistle
magic lynx
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oh wait x-4 cannot be 0 or this is undefined

stiff lily
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wavy method is identifying roots of your polynomial (in this case will be quadratic) and doing a rough sketch which pretty tells you when it's positive/negative

orchid thistle
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but how do I apply it here

stiff lily
#

multiply both sides by (x-4)^2
rearrange until you get 0 on one side

toxic ridge
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number line

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not graph

toxic ridge
orchid thistle
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but im curr trying what he said tho

toxic ridge
toxic ridge
orchid thistle
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I got x-4=0 and x+4=0 but x-4≠0 bcs it would turn into undefined

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oh wait i didnt account for the ²

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mb

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Btw im doing this right?
2x²-8x-x²+8x-16≥0
=x²-16≥0

stiff lily
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1sec

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sign for the 16 is wrong

orchid thistle
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oh

stiff lily
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ok, now factorise x^2 - 16
to identify the roots

orchid thistle
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(x-4)(x+4)

stiff lily
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where are the roots of that

orchid thistle
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x-4=0
x+4=0

stiff lily
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and x = what?
at those locations

orchid thistle
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x=4 and x=-4

stiff lily
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then identify the sign of the leading coefficient to see whether you have an upwards or downwards facing parabola

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i.e whether you'll have a
U or
n
shape

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and draw one passing through those x intercepts

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(those are the only pieces of info that matter for this)

orchid thistle
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sory 😭 but what is the leading coefficient for this?

stiff lily
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look at the term with the highest power

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in x^2 - 16

orchid thistle
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x²?

stiff lily
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and identify the coefficient

orchid thistle
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oh is x² itself alone a coefficient?

stiff lily
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no

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the coefficient is
what * x^2 = x^2

orchid thistle
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oh

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then 1?

stiff lily
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yes

orchid thistle
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positive?

stiff lily
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yes

orchid thistle
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U shape?

stiff lily
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yes

orchid thistle
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ic

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What next

stiff lily
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draw an upwards parabola passing through (-4,0) and (4,0)
it can be quite ugly and still serve its purpose

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you don't need to worry about numerical values of stuff like y intercepts, vertex or any other coordinates

orchid thistle
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im struggling 😭

stiff lily
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with this info, it should take less than 10 seconds

orchid thistle
stiff lily
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yeh

orchid thistle
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I was worried about the vertex

stiff lily
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drawing by hand, you don't need any numbers on the y-axis

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Pretty much draw a horizontal line
a vertical line for the y-axis (but you can actually ditch it)
dot your roots
and draw your curvy shape

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and with this curve, you should be able to see when your function is positive/negative

orchid thistle
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its negative from -4 to 4

stiff lily
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yes, where is it positive

orchid thistle
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-4 to -oo and 4 to oo

stiff lily
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use inf for infinity

orchid thistle
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okey, -4 to -inf and 4 to inf

stiff lily
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now you need to be a little more specific

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for the final solution

orchid thistle
stiff lily
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as it's unclear whether that includes the -4 and 4

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note that you've also you've also identified earlier the restriction that x can't be 4

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can you try stating the final solution to the inequality now

orchid thistle
stiff lily
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interval notion

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or inequality notation

orchid thistle
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The [-4,4)?

stiff lily
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that's interval notation, but that interval isn't what you want here

orchid thistle
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[-4,-inf) and (4, +inf)

stiff lily
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careful with the first interval

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lower value comes first

orchid thistle
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oh

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(-inf,-4] and (4, +inf)

stiff lily
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with interval notation, you should write

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$x \in (-\infty, -4] \cup (4,\infty)$

rocky lotusBOT
#

ℝαμOmeganato5

orchid thistle
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after this its complete 😭?

stiff lily
#

for inequality notation, you'd write
$$x\leq -4 \vee x> 4$$

rocky lotusBOT
#

ℝαμOmeganato5

stiff lily
#

yes

orchid thistle
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tyy 😭

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does' U' mean and?

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it is, wo ty

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orchid thistle
vale dockBOT
orchid thistle
#

i mean i know why it should be; x ≤ -4

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but our teacher based his on an equation like
x-4≥0
x≥4

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though cuz of that he also got x≥-4

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i wanna know if there are any other ways to get x≤-4 by means of equation

stiff lily
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annoying casework

stiff lily
orchid thistle
orchid thistle
stiff lily
#

though cuz of that he also got x≥-4
how did he get that?

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(because that'd be wrong here)

orchid thistle
stiff lily
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do you have a pic of their work

orchid thistle
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lemme send what we copied on the board

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yes i do

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this honestly just confuses me cuz it contradicts😭

stiff lily
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yeh, that middle part with 2x >= x-4 is dodgy,
ignore/erase it

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intentions of the bottom right chunk is a little unclear too

orchid thistle
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im taking notes on my personal notes so its fine

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In case our teacher insisted that he is correct then at least when he checked the notebooks I'll still be fine w the grades

stiff lily
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intentions of the bottom right chunk is a little unclear too
ok, that identifies when x-4 and x+4 are positive (for the sign table)
the sign table is missing
x+4
x-4
on the left column

orchid thistle
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oh wait lemme draw the graph that our teacher drew as well

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i forgot to copy it bcs it did contradict with our graph

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Which kind of implies that
[-4,inf) U (4,inf)

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hence the x≥-4

orchid thistle
stiff lily
#

not really,

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casework, algebra, graphical
or a mix

orchid thistle
#

this is unfortunate

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so we just leave it to logic?

stiff lily
#

wdym

orchid thistle
#

like we would use reasoning to identify the interval notation, like theres no specific methods by equation like ex.
"If x+4≥0 then
x≥-4, thus the lowest interval is greater than -4"

stiff lily
#

yes

orchid thistle
#

ight thx 😭

#

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lament flicker
#

Can anyone help number 7

vale dockBOT
lament flicker
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2^x -3^y = 5

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Solution I got (3,1) (5,3) for pair of (x,y)

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I couldn't prove that there will be no solution other than that

vale dockBOT
#
What step are you on?
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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
lament flicker
vale dockBOT
#

Show your work, and if possible, explain where you are stuck.

stark wedge
#

i was thinking that you could maybe consider both sides of the equation modulo some specific small power of 2 or 3

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but i haven't been able to find one that works

quick rose
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mod 6 gives x must be odd

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maybe that is helpful

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LTE might also work its often used in questions like these ones

lament flicker
lament flicker
quick rose
quick rose
lament flicker
#

A^n+b^n

quick rose
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yeah

lament flicker
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Like that ?

quick rose
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oh right wont work

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i switched a and b and n devastation

lament flicker
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Substituting x = 2k+1

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Then mod 4

quick rose
ebon glade
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modulo a small number cant work because there are some solutions and modulo cant tell the difference between those and possibly bigger numbers

lament flicker
#

then what should i try here

ebon glade
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dunno

quick rose
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okay so i found a solution via approach0

lament flicker
#

okay

quick rose
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should i hint u or should i send the solution

lament flicker
quick rose
#

ur problem has been posted in an AOPS thread

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and i found a solution in that thread

quick rose
lament flicker
quick rose
#

approach0 helped me find that thread

lament flicker
#

nice info

quick rose
lament flicker
#

Give me the general idea / hint so I can understand it by my self

quick rose
#

then write 5 as 32-27, factorize

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then use the fact that x and y are odd to note that x-5 and y-3 are even

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then use LTE, then FLT and some computations

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and then u arrive at a contradiction for the value of v_3((x-5)/2)

lament flicker
#

the what should i do next

quick rose
lament flicker
quick rose
#

now try to use LTE to find v_3(a)

lament flicker
#

so just v3(3)+v3(a)+v3(32) = v3(27)+v3(8)+v3(b)

quick rose
#

did you apply it directly devastation

quick rose
#

LHS is correct

lament flicker
quick rose
#

and also

quick rose
#

but in our case x-y=8

lament flicker
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yep

quick rose
#

so u cant do what u did on the RHS

lament flicker
#

wait \

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im dumb ?

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should it just be 3

quick rose
lament flicker
#

😭

#

forgor

quick rose
lament flicker
#

so 1+v3(a)+v3(32) = 3

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sorry

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so v3(a)+v3(32) = 2

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then v3(a) = 2

quick rose
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what does that tell you?

lament flicker
#

that a= 9b

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wait

quick rose
lament flicker
#

i want to say that b is not a multiply of 3

quick rose
lament flicker
quick rose
lament flicker
#

plug *

quick rose
quick rose
#

which term do you think it should be

lament flicker
#

couldnt see it

quick rose
#

well u need to do the following
4^a = 2^2a = (2^18)^(a/9) = 1 mod 19 by FLT

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reason?

  1. you just derived that 9|a, so clearly you should do something with the term containing 4^a
  2. since 9|a, a/9 is an integer which is the motivation for the 2^2a = (2^18)^(a/9) manipulation (remembering u need a power to apply FLT)
quick rose
#

now its a bunch of computations

lament flicker
#

yeah

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okay what is the next goal then

quick rose
#

do whatever the fuck this is

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i have no clue how you're supposed to think of this step

lament flicker
#

this obtained through a computation my ahh

quick rose
#

fr

lament flicker
#

i mean

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the fuck 😭

quick rose
#

fr 😭

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let me see if theres a better soln

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theres this, if u can understand this

lament flicker
#

i mean this proof is somewhat edible

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i mean is this problem imo level or just hard national level

quick rose
#

theres also something called hensels lemma which maybe usable?

lament flicker
lament flicker
#

but

lament flicker
#

i am stumped in the case that (3^(c-3)-1)=(2^(a-5)-1)

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but the more i think

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what i was thinking back then bruhh

quick rose
quick rose
lament flicker
# quick rose i see

the only problem that i found is that (2^(a-5)-1) = 27b and (3^(c-3)-1)=32b

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but

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they couldnt be posibly have the same factor right

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or their gcd is 1

lament flicker
#

one side is odd

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one side is even

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or so i thought

quick rose
lament flicker
quick rose
lament flicker
quick rose
#

why r u agreeing 💀

lament flicker
#

cuz it right ?

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nah

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im dumbing again

quick rose
#

i am very clueless about what you're doing rn

lament flicker
lament flicker
#

like

quick rose
#

i dont understand that solution xd

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i posted it to see if u could make sense of it

lament flicker
#

the only part of it where i couldnt understand

quick rose
lament flicker
#

hell no

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they all use like mod 41 or shi

quick rose
#

u need to do some order computation when it comes to exp diophantine

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but this is much better imo

lament flicker
#

MY GOD

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i found it

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yeah as i assume

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they both are coprime

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(2^(a-5) -1), (3^(c-3)-1)

quick rose
#

but what exactly are a and c again..?

lament flicker
quick rose
#

so that i can understand it

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(please pandahugg)

lament flicker
#

since you can digest all else before it

quick rose
#

oh

lament flicker
#

3^c... part = 32b

quick rose
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(why?)

lament flicker
#

hence 2^a...... = 27b

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3^c.... = 32b

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i aint writing all at

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then we know that 2^a..... is odd

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then b must be odd

quick rose
#

???

lament flicker
#

you know what

#

this prove is flawed

#

proof*

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even i cant write proeprly 😭

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cooked

quick rose
#

r u self prepping?

lament flicker
quick rose
#

thats tough

lament flicker
#

i mean

quick rose
#

check this.

lament flicker
#

alr

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hell no

quick rose
#

whats bad about the first proof 😭

lament flicker
quick rose
#

whos asking u to read the second proof

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it does explain the 757 btw

lament flicker
#

not the 757

#

the first proof

quick rose
#

yeah

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but it seems the 2nd proof generalizes better

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but ofc u cant use it in an olympiad

lament flicker
quick rose
lament flicker
#

this question shoulndt be in any olympiad right ??

quick rose
#

i think they've been asked before

lament flicker
quick rose
#

i could be wrong though u'll have to do some hunting yourself

#

not every one is as tough or involved as this one

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some are easy enough that u can argue by simply properties of primitive roots and stuff

lament flicker
#

yeah

quick rose
#

what i meant to say is dont be sad, a question like this in an oly is unlikely to be as involved

#

because olympiads usually give problems that require u to think more than crunch numbers

quick rose
#

if ur done, coose it!

lament flicker
#

.close

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small crystal
#

f(x)=(x+a)(x+b), a and b are positive constants, f(-21)>0 and f(-15)>0 and f(-18)<0, what could be a+b

vale dockBOT
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2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
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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
woeful trench
#

(Is this a multiple choice question?)

small crystal
#

i get that x=-21, -15 are outside the roots and -18 are inside the interval of roots so i got -21<-a<-18<-b<-15 or -21<-b<-18<-a<-15 but im kinda stuck from here

#

free response

#

so like i can enter any value

#

i solved it

#

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midnight pier
#

@stark wedge sorry i just noticed that you have crossed my interpretation of this expression. can you please tell me what the correct conclusion would be?

Referance (this was my statement you crossed) : "so basically for even degree polynomials, its a_(n-k)/a_n (without the negative)"

stark wedge
#

(-1)^k will still be there

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regardless if n is even or not

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the product of all roots [which means k=n] is (-1)^n a_0/a_n, and in that case for n even the (-1)^n will become 1 and disappear

midnight pier
#

but since this was a quintic we were talking about, it would be odd, so the (-1) remains right?

stark wedge
#

yes (-1)^5 = -1

midnight pier
#

okay now i understand that term in your answer

stark wedge
#

(-1)(-2)(-3)(-4)(-5) + 6 = -120+6=-114 and then you multiply that by -1 for an answer of +114

midnight pier
#

can you give me a couple scenarios to make that expression in? so i know i have it down correctly this time

stark wedge
#

hmm sure ig

#

Let f and g be defined as follows:

  • f(x) = x^7 - 4x^6 - 2x^5 + 60x^4 - 9x^3 + x^2 + 28x - 40.
  • g(x) = 5x^3 + 8x^2 + 50x - 210.

Find the sums of the following:
a) roots of f taken 3 at a time
b) roots of g taken 2 at a time
c) roots of fg taken 1 at a time (ie just the sum of the roots)

midnight pier
#

a) -60
b) 10
c) I dont understand how this works

#

you mean the terms -40 and -210?

stark wedge
#

i want the sum of the roots of the equation f(x)*g(x)=0.

#

@midnight pier

vale dockBOT
#

@midnight pier Has your question been resolved?

stark wedge
#

(sorry for the delays on my end -- i am with family rn and might not respond immediately)

midnight pier
midnight pier
stark wedge
#

a and b are correct btw, only your c is wrong

midnight pier
#

I mostly just reasoned that the highest degree term here would be x^10 (theres only one combination of terms whose product results to that term: x^7 and 5x^3, so the a_10 (a_n) would be 5.
and i need product of tersm one at a time, k=1. a_9 (is the coefficient of the term x^9: which also happens to have one way: -4x^6 * 5x^3 : so a_9 is -20.
(-1)^1 a_9/a_10 = -(-20)/5 = 4

#

ohhh theres two ways

midnight pier
#

a_9 = 8 - 20 = -12

stark wedge
#

but also you don't need to work out fg actually

#

it's just sum of roots of f + sum of roots of g that i want!

#

4 + (-8/5)

#

that's all

midnight pier
#

oh wait they'll all still have all those factors. so the multiplied polynomial will still have all those roots

#

is that a valid way of reasoning?

stark wedge
#

it's not just valid, it's exactly what i wanted from you.

#

or like

#

the recommended route

midnight pier
#

this reasoning would also work for the product of all the roots too

#

but not the other cases, right?

stark wedge
#

well actually would you like a more complicated general problem

midnight pier
stark wedge
#

right

#

gimme some time

#

let $f$ and $g$ be monic polynomials of degree $m$ and $n$ respectively, i.e.

\begin{gather*}
f(x)=x^m + a x^{m-1} + bx^{m-2} + \dots, \ g(x) = x^n + p x^{n-1} + q x^{n-2} + \dots
\end{gather*}

and let $h(x)=f(x)g(x)$.

without expanding $h(x)$, work out the sum of products of its roots taken two at a time, in terms of $a$, $b$, $p$ and $q$.

rocky lotusBOT
stark wedge
#

[you won't need any coefficients aside from the ones named!]

midnight pier
#

wait, i think i could do this!

#

q + ap + b ?

#

(btw what is a monic polynomial?)

light saddle
#

Leading coefficient is 1

stark wedge
midnight pier
#

thank you soooo much for all your help:)

#

have a nice day:))

#

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hearty belfry
#

<@&268886789983436800>, I think this counts as advertising?

static ivy
#

uhh, is this not allowed?

hearty belfry
mighty trellis
#

I'm afraid we don't allow surveys like this. If you'd like to appeal that you should ask @feral pebble

#

I'm going to remove your poll now, apologies.

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static ivy
#

.close

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grave kernel
#

@ruby sleet hey im back can you please teach me what you were teaching me yesterday sorry for the ping

grave kernel
#

for the table

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fiery estuary
#

can someone explain to me why shifting the negative exponents from the denominator to the numerator works? I understand dropping the n^-2 to the denominator, because n^-2 is just 1/n^2, but i dont understand how m^-4 and n^-3 shifted to the numerator and became m^4n^3

hot tide
#

$\frac{1}{\frac{1}{x}} = x$

rocky lotusBOT
#

artemetra

fiery estuary
#

so basically this

hot tide
fiery estuary
#

o yeah ur right

#

m at the end

hot tide
hot tide
fiery estuary
#

okay thanks

#

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left fiber
vale dockBOT
hearty belfry
#

!status

vale dockBOT
#
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
pure mirage
midnight pier
#

Show ur work

#

What did u try

left fiber
#

from here i could probably try by-parts right?

#

u=1+sinx

wraith heart
#

or try v = sqrt(u) and then partial fractions

tribal tiger
#

i think its better way

left fiber
tribal tiger
#

its classic integal

left fiber
#

okay

#

thx guys

#

how do i close this now

#

.close

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solar flame
#

How many months would this take to finish?

wraith heart
light saddle
#

more than 6 weeks lol

solar flame
wraith heart
solar flame
#

My bad if it doesn’t

stark wedge
#

help channels are for specific math problems

solar flame
#

Oh alright

stark wedge
#

youre being redirected to a channel where your question is more appropriate

solar flame
#

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midnight pier
vale dockBOT
midnight pier
#

how to do this integral

magic lynx
#

oh god

#

doesn't look pretty

midnight pier
#

ye

magic lynx
#

uh in seriousness though

#

let us try u-sub=(e^x+x+1)^2

midnight pier
#

not gonna work

#

we dont have derivative in numerator

magic lynx
#

uhh du=2(e^x+x+1)(e^x+1)

#

ohh wait

#

here

#

i give you related integral

#

Calculate $\int\frac{(e^x+x+1)^2-(x^2+x)}{(e^x+x+1)^2}\mathrm{d}x$

rocky lotusBOT
#

Arnavutköy

magic lynx
#

now try u-sub

#

with u=(e^x+x+1)^2

somber sequoia
#

judging by the structure this was the result of some sort of quotient rule application

midnight pier
#

yes

#

i tried that kind of reverse engineerign

#

but that didnt work

midnight pier
somber sequoia
#

[ \int \frac{x^2}{(e^x + x + 1)^2} \dd{x} + \int \frac{e^x + x + 1}{(e^x + x + 1)^2} \dd{x} - \int \frac{e^x + 1}{(e^x + x + 1)^2} \dd{x} ]

midnight pier
#

doesnt work kinda

jade ivy
somber sequoia
#

@midnight pier try integrating the first integral by parts

#

I suspect it will cancel out with the second one

#

or vice versa

midnight pier
#

oh alr

somber sequoia
#

The third integral can be done with a substitution

rocky lotusBOT
#

maison

midnight pier
#

second and third ar easy

somber sequoia
#

the second one by itself is probably non elementary

midnight pier
#

but what should be hte first function adn the second funtion for by parts

#

of the first one

distant pulsar
#

you can’t integrate the first one

#

at all

midnight pier
#

how do i see these kinda things

somber sequoia
midnight pier
#

like hwo do i check if i can integrate something or not

somber sequoia
#

it should cancel out with the first hopefully

magic lynx
#

uh i am looking at the solution at integral-calculator.net and i can assure you that I would have never come up with this nor half of the people in the mit integration bee

somber sequoia
somber sequoia
midnight pier
#

o

#

no

magic lynx
#

do you want to know what to rewrite it as

midnight pier
#

like what should be the first and second function for by parts

#

in the first term

somber sequoia
#

leave the first term

#

work on the second one

#

integrate 1 and differentiate 1/(e^x + x + 1)

jade ivy
#

Its a rational function of x's and e^x's without any weird nth roots or infinite sums. You are not giving people on an MIT Integration Bee enough credit.

midnight pier
#

ok

jade ivy
#

Even if this turned into a messy integral involving a bunch if dilogarithms it would not be out of reach of a group like that

magic lynx
#

(in competition conditions i claim)

#

with like half an hour yes

distant pulsar
#

half an hour? this is doable in less, which is expected of integral problems

somber sequoia
#

it can be done quick

distant pulsar
#

okay now that i certainly disagree with

#

the approach you suggested is not even correct

somber sequoia
#

on my JEE shift there was a similar problem except the reverse-IBP twice

somber sequoia
midnight pier
#

I did it but it's doesn't cancel our

distant pulsar
magic lynx
midnight pier
#

This is also a jee question

distant pulsar
#

it just comes down to testing things

magic lynx
#

hopefully not mains

midnight pier
#

not mains

magic lynx
midnight pier
#

no

#

i dont know the options

#

but my teacher said taht

somber sequoia
#

wait just combine it now

#

you can factor the x out

#

and reduce the power in the denom

magic lynx
#

essentially you only get this through guess and check in jee exam format

somber sequoia
#

also idt that should be a - sign right

#

you get a - from the IBP and one from the derivative

#

so it becomes a +

distant pulsar
#

you can notice i.e. $\frac{\mathrm{d}}{\mathrm{d}x} \frac{x}{D} = \frac{(1 - x)e^x + 1}{D^2}$, $\frac{\mathrm{d}}{\mathrm{d}x} \frac{1}{D} = -\frac{e^x + 1}{D^2}$

rocky lotusBOT
#

Mqnic_

midnight pier
#

Idts

fallen mesa
#

,rotate

rocky lotusBOT
distant pulsar
# rocky lotus **Mqnic\_**

from here, you find $\frac{x^2 + x}{D^2} = (x + 1)\frac{\mathrm{d}}{\mathrm{d}x}\frac{x}{D} + (1 - x^2)\frac{\mathrm{d}}{\mathrm{d}x}\frac{1}{D}$

rocky lotusBOT
#

Mqnic_

distant pulsar
#

and now you integrate by parts

somber sequoia
distant pulsar
#

you are done

midnight pier
#

I mean by parts give minus sign for the second term

somber sequoia
#

and the derivative gives you another one

midnight pier
#

Oh yee

#

I am sorry

#

Now how do I integrate this

frozen ledge
#

dude isn’t even reading manics messages

midnight pier
#

i am

somber sequoia
#

probably multiplying with e^-x

distant pulsar
somber sequoia
distant pulsar
#

which gives you the answer essentially immediately

somber sequoia
#

ah yeah that works better

midnight pier
#

Yes

#

Thanks guys

#

Ik I am disturbing but can I ask another one

#

like i was trying asinx+bsinx property but still not getting the correct answer

somber sequoia
#

hmm

#

I have a bit of a crazy idea

midnight pier
#

i tried reverse engineering also by quotient rule

magic lynx
midnight pier
#

thx 😁

somber sequoia
#

[ \int \frac{\tan^2 u}{(\sin u \sin \tan u + \cos u \cos \tan u)^2} \dd{u} ]

rocky lotusBOT
#

maison

somber sequoia
#

now the denominator is cos(u - tan u)

#

tan^2 u = 1 - sec^2 u

#

badabing badabong

midnight pier
#

u substituted x as tant

somber sequoia
#

yes

#

I guess it wasn't a crazy idea after all

#

I've seen the xsin(x) + cos(x) structure in an integration bee before and I used the same technique

midnight pier
#

should nt there be a cos^2x in the denominator

somber sequoia
somber sequoia
midnight pier
#

Yes I got it

#

Now what should I do

somber sequoia
#

in the denominator use the cos(A - B) formula

#

and rewrite the top using the pythagorean identity

midnight pier
#

This ??

somber sequoia
#

yeah

#

but write it as sec^2 u - 1

midnight pier
#

oh

somber sequoia
#

you probably see what can be done now

#

also there should be a ^2 over the cos (t - tan t)

midnight pier
#

Oh yes

#

Sorry

#

Sorry but I can't think of what should I do next

#

Tant as v

#

?

rocky lotusBOT
#

maison

somber sequoia
#

👀

midnight pier
#

I got this

#

But what should I do after this

somber sequoia
midnight pier
#

Tant-t

#

Ohhh

somber sequoia
#

yes

midnight pier
#

Oh my god

#

I am so stupid

somber sequoia
#

because the derivative is on top

midnight pier
#

But like how did u thought so much out of the box

#

I would have never thought in this manner

somber sequoia
#

you'll get there with practice

#

integration was my favourite chapter in all of JEE i had a bit of an obsession

midnight pier
#

Same

#

It's my fav too

#

I am a jee student

somber sequoia
#

good luck lol

fallen mesa
#

I made all my classmates and my teacher to sign a petition to remove integrals chapter from the syllabus

#

On our blackboard

midnight pier
#

I love it

#

I hate chem tho

#

Other than physical chem

#

hey @maison canu recommend me some great integration books

#

i need some guidance in it

#

i am currentyl doing modules and cengage sometimes

vale dockBOT
#

@midnight pier Has your question been resolved?

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brave urchin
#

is there some algorithm to follow so i can remember the 20 something integrals formulas? for derivatives it's kind of easy, even with composed functions, but for integrals it just looks random to me. i'm attepmting to learn them on my own during summer break.

ebon glade
#

wdym 20 something integral formulas

charred nacelle
#

Just practice questions

ebon glade
#

the easy integrals are just reverse of basic derivatives

charred nacelle
#

Also some formulas have same things but just a few changes which can be easily remembered

steady charm
#

unlike for derivatives, there isn't a general algorithm that works for all integrals

ebon glade
#

and then its just u-sub and ibp

steady charm
#

-# technically there sort of is one but it's like 100 pages

fallen mesa
#

Integral of tan is ln |cos| and ln |sec|

ebon glade
#

-ln|cosx|

vale dockBOT
#

@brave urchin Has your question been resolved?

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humble flicker
#

does someone mind helping me find out why the answer is B here? i guessed it

humble flicker
#

they have this solution/working out

#

but is R the range?

warm kayak
#

they're asking the y coordinate of B, which is the maximum value of the function

timid wagon
#

have you dy/dx yet?

humble flicker
#

but what do i do from there

timid wagon
#

if it's a turning point what do we do

warm kayak
#

the maximum of acosx + bsinx is root(a^2 + b^2)

timid wagon
timid wagon
humble flicker
#

then solve

#

then test if it’s a max or min using second diff or sign table

#

then u get 2 -3tanx right

#

if u divide everything by cos

timid wagon
#

then you solve for x

humble flicker
#

but x = 0.58800…

#

oh do u sub it back into y?

timid wagon
#

that'll be your y value

#

but make sure you sub back into the original equation

humble flicker
#

now i got 3.6055…

#

yea

timid wagon
humble flicker
#

oh it’s the same

timid wagon
#

notice how sqrt13 = 3.6

#

yep

humble flicker
#

yea

timid wagon
#

there ya go

humble flicker
#

my calculator just didn’t convert it to sqrt13

#

so i didn’t know beforehand

timid wagon
#

yup

#

no worries

river shale
#

Never seen this method before

#

Dawg

timid wagon
humble flicker
#

max point?

timid wagon
#

what you've done is a troubling way

humble flicker
timid wagon
#

you can search it up

humble flicker
#

compound angles?

#

wait no

timid wagon
#

or just type the formula out on google

#

you should get plenty of explanations

humble flicker
#

oh it’s the R-method

#

forgot abt that

#

okay thanks

#

.close

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#
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grand nova
vale dockBOT
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whole torrent
#

sinx (x in radians) = sinx (x in degrees)

What's the value of x (x isn't equal to 0)

tidal terrace
whole torrent
#

so sin(xpi/180) = sinx right?

tidal terrace
whole torrent
waxen scarab
rocky lotusBOT
#

Sherif Player

waxen scarab
#

Where k is an integer

whole torrent
#

So x = 2kπ ((π/180) - 1) ?

waxen scarab
#

Actually
$$\pi x = 180x+360k\pi$$
$$\pi x - 180x = 360k\pi$$
$$x(\pi-180)=360k\pi$$
$$x=\frac{360k\pi}{\pi-180}$$

rocky lotusBOT
#

Sherif Player

whole torrent
#

Oh thank you, trigonometry is confusing but i understood it

waxen scarab
#

Do you understand why did we solve for that specific equation?

whole torrent
#

Not actually

waxen scarab
#

For any trig function in the units of radians
f(x) = f(x+2kπ)
like
sin(x) = sin(x+2kπ)
And so on
Because 2π resembles a full revolution

#

So if we revolved the angle around k full revolutions it would still remain the same

#

Do you understand now?

#

There are actually more solutions to the system of sin because sin has another property which is
-sin(x) = sin(-x)
Which would be a bit harder to solve

whole torrent
#

Yeah, i understood it but i have a question. Is it because 2pi is period of sinx?

waxen scarab
#

Yes

whole torrent
waxen scarab
whole torrent
#

Okay i understood it

#

Thank you so much

waxen scarab
#

Do you have any other questions?

#

By the way, I tried it here and it worked

whole torrent
whole torrent
waxen scarab
vale dockBOT
#

If you are done with this channel, please mark your problem as solved by typing .close

whole torrent
#

.close

vale dockBOT
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thorn kernel
vale dockBOT
thorn kernel
#

how do we draw this again?
for k = 1 we get y = +-3z whic hi get the 2 lines
but the parabolas how do we draw those

#

anyone know how and why?

chrome beacon
#

examine y = 0 and examine z = 0

thorn kernel
#

z = +-1/3

chrome beacon
#

yep so those are the peaks of those hyperbolas

thorn kernel
#

i did that but what does that gotta do with anything

#

but how do i know to draw parabolas

#

at thsoe points

#

is what im asking

chrome beacon
#

they're not parabolas sad_02

#

they're hyperbolas

thorn kernel
#

in the zy plane yea where x = k

chrome beacon
#

but yeah you know they're hyperbolas because they follow the form $az^2 - by^2 = 1$

rocky lotusBOT
#

not haylee

thorn kernel
#

hm ok so this is just memorization

#

also what the fuck does the k = 1 thing have to do with the full hyperparabola

chrome beacon
#

kinda yeah. it's a common conic section

chrome beacon
#

it's a degenerate hyperbola

#

these are conic sections, have you seen this before?

#

3 is a hyperbola

#

1 is a parabola and 2 is an ellipse

#

the crossed lines are what happens when the plane in 3 crosses the centre point

thorn kernel
#

ok but we

#

use teh 2 y=k and x=k

#

to draw the hyperparabola

#

right

chrome beacon
#

do i need to automod the word hyperparabola

#

hyperbola

thorn kernel
#

same thing

#

yk what i mean

chrome beacon
#

it's degenerate when it's of the form $az^2 - by^2 = 0$

rocky lotusBOT
#

not haylee

chrome beacon
#

so by setting k = 1 the right side becomes 0 and you get the degenerate case

thorn kernel
#

so is this the math rage bait

chrome beacon
#

?

thorn kernel
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anyways

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so for the y=k i understand this right

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we draw circles

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but im confused about the x=k

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how to incorporate what we drew on that 2d plane here

chrome beacon
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well the crossed lines is what happens when k = 1

thorn kernel
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so the top and bottom are lik this i get right

thorn kernel
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or the sides

chrome beacon
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oh i see what you mean

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imagine you have that hyperboloid (boomerang looking thing)

thorn kernel
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oh wait i think i get

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the sides are done

chrome beacon
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and you look at it from the side so kinda like you've drawn indeed yea

thorn kernel
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just the 2 crosses left

chrome beacon
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well the shape you've drawn is for k = 0

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it'll look different for k = 1

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in particular its waist will be fully snatched and drawn in to a point

thorn kernel
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i mean this is the answer

chrome beacon
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yes, most of the time it looks like pictured

thorn kernel
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where is the crosses incorporated here in the pic

chrome beacon
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i would recommend using desmos 3d to draw this shape

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and add a slider for k

thorn kernel
chrome beacon
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oh hang on

thorn kernel
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this looks nothing like my graph answer what?? in the zy plane

chrome beacon
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okay i see, i think the crossed lines happen when the plane youre looking at is tangent to the inner waist of the hyperbola

thorn kernel
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tbh i dont think it matters

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just memorize it

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thanks tho

chrome beacon
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if this is where you take your projection

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you can see the crossed lines

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(i got this by plotting x = 1 and hitting "extend to 3d")

thorn kernel
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but now u dont see teh side parabolas

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or is that cuz desmos cut it off

chrome beacon
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this has a slider

chrome beacon
thorn kernel
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oh wait nvm

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i see it

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was talking bout this

chrome beacon
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after playing with it in the graph view, do you see how the hyperbola gets drawn tighter until it becomes a pair of crossed lines?

thorn kernel
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yep

vale dockBOT
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@thorn kernel Has your question been resolved?

vale dockBOT
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surreal sinew
#

Hey everyone

vale dockBOT
glass kelp
#

hello

surreal sinew
#

How is this a "legal" move:

surreal sinew
glass kelp
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[ \sqrt{x^2} = |x|]

rocky lotusBOT
surreal sinew
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Yes ik

lyric sundial
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Then what? 😅

surreal sinew
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But |x|≠-x

jovial edge
#

because when it goes to negative infinity, it's negative

surreal sinew
glass kelp
#

what

lyric sundial
glass kelp
jovial edge
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If $a<0$ then $|a|=-a$ isn't it

rocky lotusBOT
#

Alexis_Fx

surreal sinew
#

Oh wait

rocky lotusBOT
lyric sundial
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Yes

surreal sinew
#

That's true

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Oh I get it

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If x is negative then the absolute value is -x

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Makes sense

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Ok sorry haha

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Thank you guys

surreal sinew
#

.close

vale dockBOT
#
Channel closed

Closed by @surreal sinew

Use .reopen if this was a mistake.

vale dockBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
After 15 minutes, feel free to ping <@&286206848099549185>.
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• Be polite and have a nice day!

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verbal sentinel
#

dont undersand

vale dockBOT
stark wedge
#

show the full question.

verbal sentinel
stark wedge
#

ok, so then

final adder
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did you do part a?

verbal sentinel
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i need help on part b