#help-13
1 messages · Page 331 of 1
you could memorize but i different question of same type would confuse you
is this correct
....
give me a sec
Nope
That P(A|B) = P(A intersection B)
thats not P(A|B)
thats P(A intersection B)
anyone
short answer I do not
..
oh
is the intersection just P(a) X P(b)?
have you learnt about sets yet?
yes but I don't necessarily remember everything
that is only when the given sets are independant
not always
what does this symbol mean?
a subset
B is a subset of A
for the second one
it is true only when two events are independant
and how do we know that it is independant?
.
it will be given in the question
this
nevermind I see it now
P(a int b) = P(a)xP(b)
I fully unstand ii)
okay but honestly
for third one
Kay
I was going off this formula
..
so does that mean this is true?
yes
and if yes, this is what I had trouble understanding
alright ty for helping so far
btw for the third one
they have to be mutually exclusive events
so
P(a int b) = 0
and thus the answer is zero
got it
nice
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my pleasure
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,rotate
!status
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
gaussian elimination has something to do with matrices
so you want to make those equations into a matrix
no?
do u have the system written down as a matrix?
why did your first row change
idk help
what did u do to get the second matrix
the elementary operations used^
row echolean (can't spell)
yeah can u tell exactly what u did?
yes it makes sense
R1 - R2 should be
1 - 0 -2 - (-1) 1 - 1 3 - 1
1 -1 0 2
this is okay
u subtracted 3R1 from R2 and u get R2 as u have written in the second matrix
for this u must subtract the R2 u just got, from R1
ok, what's the next step then?? 😶🌫️
done
but uve done the subtraction wrong
really
this is what it must be
nah i just did -3 wrong in R1
idk cuz this is from my tutor and i haven't learnt from school yet
so im just kinda fonfused
confused
yes -3 is wrong, that must be -1 there
yes but i don't see anything wrong with my R2
R2 is correct
anyways let's say i got to ur step, what to do next?
so u have -y + z = 1, and then x - y = 2
oh so I don't get numbers
u dont because there arent enough equations
so u can let z = t or something, like u said here
and then in terms of that z, u can solve for x and y
how do i use it to do (b)
it says "Hence"
meaning i must use ans from (a)
wait OK I got it
thanks @lusty grotto
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I’m going to take a test today and I’m going to ask here because it’s a lot easier to get explained things but what are functions they teach you originally like exponential linear and all that and how do you change the y-intercept and all that on the equation
You should not ask things here during the test. I think that's against the rules
You can clarify after test
Im going to

?
^^
It says I’m going to take a test
And that test is in like
An hour and a half
You can ask doubts before your test starts. But during the test you can't ask questions here as that can be considered cheating
Yeah the test hasn’t started dude 😭
??
What are the main functions and how do you change them
Or more so
Translate them
Referring to the first algebra ones such as linear, quadratic, and expontential
⁉️
wdym translate them
What you are asking is broad , you gotta be more specific
Up 2 right 3
Like if I had an exponential equation
Or I’m not sure of another example
And I were to want to make the y-intercept down 2 and translate it right 3
How would I change the equation to do that
Ohhhh stretching graph
to change the y intercept, you add the function with some constant
so f(x) + 2 means up 2
horizontal movement you change its input
f(x-2) means right 2
f(x+2) left 2
so i guess thats for an exponential function 2^x
Yes
thats moving it up 2 and right 2
Alright thanks that helps is it the same for the other equations?
yes
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Hey! Sorry To Ask some simple questions, but I cannot understand questions (2), (3), and (4) Can somone help me?
construct one line parallel to l and m for each of the intermediate angles i guess
yeah, i got that, but i dont know what to do after that.
ah i remember
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I dont understand the different between these two functions
well, one of them is not a function 
Should I think of it like a piecewise function?
Arent both like that though
Im confused on why the graph changes depending on where the modulus is
<@&286206848099549185>
well your absolute function is on different variables
you can think of it as a piecewise function
this is not
possible
by definition of the absolute function you wont get anything
What would the ranges be?
You are right, the function isnt negative there
But, how are we getting the negative value
sorry, I dont really understand what you are saying
like the negative value of y?
yea in essence that works as a piecewise function
so for y<0, y=x-1, and for y=>0, y=1-x
Would I be able to make it piecewise on the basis of x? like when x > c, y = 1 - x or something?
you can see that the x-1 and 1-x are conjugates
yes you can
just put a constant inside the absolute function
so abs(x-c)=something
if x=>c, x-c is non negative
I meant when $|y| = x - 1$, Could I make this a piece wise on the basis of x, or is that not possible?
Adarsh
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a, b, c are linearly independent vectors.
r = xî + yĵ + zk̂. Express r as a linear combination of a, b, c.
well I did
r = αa + βb + γc
now let n1 = b x c n2 = a x c n3 = a x b
so
α = r⋅n1/a⋅n1
β = r⋅n2/b⋅n2
γ = r⋅n3/c⋅n3
and finally
r = (r⋅n1/a⋅n1)a + (r⋅n2/b⋅n2)b + (r⋅n3/c⋅n3)c
now my teacher said that from this result we can derive the cramers rule or this is basically the cramers rule, which is the thing i dont understand
like, am i supposed to put n1 n2 n3 and then expand the whole thing
but even so how is this related to cramers rule
@sonic flicker Has your question been resolved?
<@&286206848099549185>
@sonic flicker Has your question been resolved?
what
@sonic flicker Has your question been resolved?
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what is the probability that the 50th card drawn from a deck of 52 cards is the 4th ace?
i did probability of getting 3 aces in 49 cards = (4c3*48c46)/(52c49)
and then out of the rest 3 theres 1/3 chance of it being ace
so multiplying it comes close to 1/5
but my question is.. the probability of 50th card being an ace itself is 1/13?
so shouldnt the odds of that being the last ace be lesser
,w (4C3)*(48C46)/(52C49)
this times 1/3 is about .07, less than 1/13
OH thank you! also last question can i just multiply the 1/3 with it? are the events independent?
it's less about independence and more that there's some hidden conditioning being done
what you're calculating is P(3 aces in first 49)*P(50th is an ace | 3 aces in first 49)
you can read the original question as P(3 aces in first 49 and 4th ace on the 50th) and then you're just applying the definition of conditional probability
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Hello, i need help
your first box has 2 pis
those i have no idea but i imagine whoever wrote the questions messed up
oh wait, lol i can't read
you're supposed to answer in cm, not m
ohh
so im supposed to do conversion
r = 200 cm
h = 200 cm
?
That was correct, Nice. Thanks:)
.close
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I'm not sure how to do this
Do you know the condition for a quadratic equation to have distinct real roots?
yeah
the
discriminant
must be 0 or greater
wait
(k+1) is supposed to be the coefficient of x^2?
Yes
Notice the roots have to be distinct
meaning?
What happens when D = 0
Yea
oh I see
let me use the formula brb
wait
how am I supposed to use the formula
when its k+1
a = k+1
What's the formula for D
b^2 - 4ac
What's b?
You sure?
Uhh I havent tried
Why first term negative
because I multiplied by -4k
Can you mention your a b and c
nah wait
Try computing it again
dude
i got
16k^2-36k-36
find roots of k
Okay
This would be equal to 0 or what?
They gave distinct roots
how do we know it equals 0
discriminant > 0
if it is equal to zero
It's not
yes
.
why is discriminant zero
for distinct roots
is the qustion to find the roots of the polynomial
this
It is not zero now, but if it is zero, then the roots of the equation are equal and real
tyler is correct equate the discriminant to be >0
You found out the discriminant and you know you have to make D > 0 for distinct real roots
okay
Can you solve this: 16k^2-36k-36 > 0
divide it by 4 on both sides to make it easier
4k^2 - 18k - 18
then, x = (-b +- discriminant)/2a
no
oh mb i divided by 2
36/4 ≠ 18
Yup
4k^2 -9k -9
Yes and that is greater than 0
okay
Yup
should I factorise?
okay, do it on a paper and send a pic if you want to
ok so
2(2k^2-9k-9)
wdym
you want help?
I edited it
still wrong
it isnt tho
how is it correct?
if you take 2 common, you take it from all three of them
and why would you ever want to take 2 common
whats the use
ok ok lemme help you
nothing ig
and you don't need to take common
did you not learn factorisation yet?
(4k+3)(k-3)
=>4k²-9k-9
=>4k²-12k+3k-9
=>4k(k-3)+3(k-3)
=>(4k+3)(k-3)
these are the steps
ik
bruh
is?
-0.75 < k < 3
ig
this is wrong
idk lol
Now that you factorized it
You have to find k for which (4k+3)(k-3) > 0
Yup
divide by k-3
So the way you find the range of values for k is
You have 3 options
k < -0.75
-0.75 < k < 3
k > 3
The nature of the sign of the expression would alternate between these ranges
nvm
So you can pick any and find its behavior
how come
Hmmm
magic
Do you know inequalities?
Like if ab > 0
then either both a and b are positive
Or both negative
yes
Ok so if you try to make both of them positive
It would mean 4k + 3 > 0 as well as k-3 > 0 yeah?
Remember we're trying to solve this
dude continue
Yeah so
that can happen when k > -3/4 as well as k > 3 which means k > 3
yup
but thats stil wrong
No no
nuh uh
i meant
.
k greater than -3/4
It's not that straightforward
ye ye
Ok lets take an easy example
sure
ok
yh
yes
If you want to just solve it boom then
what? 😭
You just need to know that the first range is positive, the second is negative and it keeps alternating
boom then
uh is this always the case?
yeah unless the root repeats
wavy curve method
Yup
We go to our example and try to understand in simpler ways hopefully
Yup yup
So uh (k-2)(k-4) > 0
@last mango topper.. genius.. prodigy
for ab > 0 we know it only happens either if you have:
a>0 as well as b>0
OR
a<0 as well as b<0
oki?
oki
yes
@floral tundra Lmk if you struggle somewhere, I'd stop
nah its alr
clear so far
continue
Lmao dude
he didnt ask u 😭 🙏
ik
carry on
yup
So lets try both the cases
First we go with a>0 as well as b>0
mhm
So k-2>0 AS WELL AS k-4>0
mhm
Yeah but we have to satisfy both the conditions
yes
If you need help unrelated to this, refer to #❓how-to-get-help
aww
carry on
yup
If k needs to be greater than 2 as well as k need to be greater than 4
yup
Then it means it has to be greater than 4
yup
it won't satisfy both
yup
It wont satisfy both right?
k>4
So thats why it has to be greater than the bigger number of the 2 and 4
the other way around, k<2
yes
I get it
carry on
now lets do the actual question
Oki
Oki
Oki
aww
So (k+0.75)(k-3) > 0
its alright
So for the first case: ab>0 => a>0 as well as b>0
k > -0.75 as well as k > 3 and since we need to satisy both, it has to be k > 3
for the second case: ab>0 => a<0 as well as b<0
k < -0.75 as well as k < 3 and since we need to satisy both, it has to be k < -0.75
So yeah together we have the entire range of values for k
k < -0.75 or k > 3
oh so
Yeah
i understand
Yup
good
yup
Which one are you talking about?
ab>0
a>0,b>0
a<0,b<0
so it cant be the first one
Only if it's bigger than 3
cuz that would be ab < 0
explain it again please
why is k smaller than -0.75
im confused bcs
we got the answer to be
Because remember
k is greater
yeah?
Greater than ?
-0.75
No
Can we do the (k-2)(k-4) for simplicity? then u just switch 2 with -0.75 and 4 with 3
ok
So if we want ab to be > 0 then we either need
a>0 AND b>0
OR
a<0 AND b<0
So now first case is a>0 AND b>0
Where k-2 >0 as well as k-4> 0
k-2>0 is true for all k > 2
k-4>0 is true for all k>4
that works
But since we want both of them to be true simultaneously
k just has to be greater than 4
yea
NOW second case
a<0 as well as b<0
Because that is also part of the solution right
yh
So we need k-2<0 as well as k-4<0
First is true for all k<2
And second is true for all k< 4
Since we want both to be true together
It's true for all k< 2
ok
So we found out we can either put any k which is less than 2
Or any k that is greater than 4
Right?
But not in between
Because if you put any k which lies in between 2 and 4 (like 3) then it would make the expression negative
But we want it positive (>0)
🌊, for aisha
1st half
okay
Like yk
but both part of solution?
either this or that
ah okay
ab>0 is true if:
yhyh i get it
yup
.
ok
so
If you get this, i think you can also get the answer to your original question
now with our question
bruh
It's fine. let them be haha
k>3 and b>-0.75
.
Aisha
ohh
look
so this
No
Oh ok so are you solving first half? like the a>0 and b>0? if so, then yess
yes
yes
k>3 AND k>-0.75 => k>3
OR
k<3 AND k<-0.75
Now what about the second one
here
yup
thats the first half no?
both
okay
There are 2 lines
One above AND is solved
One below is left
k<3 AND k<-0.75 this one
ok
yup
OH
k is bigger than three(first part)
2 parts
yup
1 part the solution is k>3 and the other is k<-0.75
YES!
too easy
But the final answer
😭
They have to be mentioned with a union
Yup
(-inf,-0.75) U (3,inf)
true
Union means it can belong to either of the ranges
yup
okay so
inf = infinity
open brackets only
Uh thats the answer basically lol
this?
yup
yup
.
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thanks btw tho
his pleasure
well the common way of writing it is what he told
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could anyone tell me what g'(x) is equal to ?
im not sure about what exactly am i supposed to do here
the f is annoying
Can you differentiate f(x)?
im guessing since youre not given the equation for f (also i cant read... french i think?) youre just supposed to give the derivative of g(x) in terms of f(x)
or does that say at point 3?
Let me translate it
Deteremine the equation of the curve Cg at the abscissa point 3
yes
does it give you anything else?
only this
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can i get help?
determine the limit
i found that the limit is 8
however
can i verify it by doing this=
this is h->0
but im wondering if i can add 1 and -1 to verify
the teacher wants us to verify
and not with derivative
can i please get help with this?
I dont have that much time before the due date
no you can't
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yeah
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Does $\mathbb{R}(i) = \mathbb{C}?$
bboy
yes
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heelp with this pls
@static knot Has your question been resolved?
@static knot Has your question been resolved?
.close
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why did my teacher not get 1/1+sin(x)
in the video he was like "take the derivative of the top, then take the derivative of the bottom"
but that isnt how derivatives work
you have to use the quotient rule right?
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I need a walkthrough on how to solve this please, if it can be solved. I have two points: (282.02 , 2.6096x10^-4) and (286.15 , 1.887122x10^-3).
Is there something I can do to create a logarithmic function that passes through both?
Sup 👋
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if an entire quadratic equation is >= 0 means it either has no REAL roots or exactly 1 root
am I right?
‘or 1 real root of multiplicity two,’ but yes
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this like ai which is dumb
someone promoting it to me
not really AI has gotten pretty good
It’s still not completely reliable
ofc not, but neither are ppl
still sounds like it is correct but has stupid mistakes lol
I find it is more confidently wrong than people are, especially in a semi public place like here where if you give a wrong answer someone will likely chime in
For example your ai response is actually wrong, but it looks convincing
In the third case if the discriminant of a parabola is >0 there are two distinct roots. There cannot be a repeated root
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I have a group theory question
I'm trying to prove if n = 2, 4 , p^r, 2p^r then U(n) is cyclic
Ive looked at some proofs and the part I keep getting stuck on is
The justification for U(4) being cyclic
Particularly where this part came from
@hoary charm Has your question been resolved?
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Let ( a_n = \int_{0}^{n\pi} x|\sin x| , dx ), where ( n = 1, 2, \cdots ), how to find the expression for ( a_n )?
Scoria
@eager hemlock Has your question been resolved?
can u use integration by part, let u=x v'=sinx, im not sure if the absolute value is important
i think you can just find $\int_{0}^{n\pi} x\sin x , dx$ by IBP and then flip the signs every $\pi$
Luke
Try finding $\int_{(n-1)\pi}^{n\pi} x\sin x , dx$ for odd $n$
Luke
and flip the sign for even $n$
Luke
I don't quite understand [flip the signs for every pi] ..could you maybe elaborate a bit?
@eager hemlock Has your question been resolved?
Sorry just saw this
When is x sin x positive?
It should be positive from 0 to pi, 2pi to 3pi, 4pi to 5pi
And so on
It should be negative from pi to 2pi, 3pi to 4pi, and so on
$\int_{0}^{\pi} x\sin x , dx-\int_{\pi}^{2\pi} x\sin x , dx+ \int_{2\pi}^{3\pi} x\sin x , dx-\cdots$
Luke
Try evaluating each term
$\int_0^{\pi} x \sin x , dx = \left. -x \cos x \right|_0^{\pi} + \int_0^{\pi} \cos x , dx = \pi$
Scoria
Do you see why we keep alternating between adding and subtracting
ye since |sinx|
$\int_{k\pi}^{(k+1)\pi} x (-\sin x) , dx = -\int_{k\pi}^{(k+1)\pi} x \sin x , dx.$ for k odd
Yep
Scoria
Now find $\int_{(k-1)\pi}^{k\pi} x\sin x , dx$
Luke
For k odd and k even
$\int_{(k-1)\pi}^{k\pi} x \sin x , dx = -x \cos x|{(k-1)\pi}^{k\pi} + \int{(k-1)\pi}^{k\pi} \cos x , dx = -[k\pi \cos(k\pi) - (k-1)\pi \cos((k-1)\pi)] + [\sin(k\pi) - \sin((k-1)\pi)]$
Scoria
@patent ivy I'm not sure if this is the right track..
Notice how the sins go away since they are multiples of pi
Let’s say k is odd
Then the expression becomes
for k= odd, this integral is -k\pi+(k-1)\pi-0
I think it should be $(2k-1)\pi$
Luke
for k= even, this integral is -[k\pi+(k-1)\pi]+[0-0]
So we get -(2k-1)\pi
So it turns out this becomes $\pi+3\pi+5\pi+\cdots$
Luke
yes ..
thank you
btw any other easier method?
Ok thank you so much luke ! @patent ivy
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To be honest I’m not sure 😅
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hi guys im watching a math video about differential equations, but i don't understand where they get y^2/2 on the fifth row
and the x^2/2 as well
ren
same goes for x and y
ohh that's the rule?
it's just an integral-
don't start with differential equations if you haven't done integrals yet
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If i had to determine the domain of this graph, I would say (-3, -1,2) U (0,9)
what do you guys think
!occupied


