#help-19
1 messages · Page 59 of 1
I mean, it's possible that c = 0 but you cannot infer that from the statement that y=x is a tangent
I get that
duh you guys are right
ok but i still do not understand why y'(0)=1
y' gives the slope of the tangent at point x
since you are given that the tangent at the origin is y = 1 * x, it follows that y'(0) = 1
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hello I need some help with this symbol manipulation problem
I originially thought of distributing the m, but how would that work if there's another variable inside the parenthesis
or maybe I don't do that at all, I'm kind of confused
I could try to subtract 2, but how would that work? Would I just but it outside the fraction?
so something like this?
and then make it positve x
I'm not sure if I was just supposed to make everything inside the fraction negative or just write a negative sign outside
no, you did it correctly
you could also negate the things inside the fraction, it would be the same
$-\frac{3-y}{m}=\frac{-(3-y)}{m}=\frac{y-3}{m}$
kheerii
notice how the - sign went to the numerator?
yes how come it didn't also go to the denominator
it can
but that won't be constructive
alright thanks for the help, I totally forgot you could just divide both sides instead of distributing
.close
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Did I even do any right
First is incorrect
What was the answer
I don't know but it can be only i dot
You should solve it
Multiply by 2/3
I guess
If previous steps were correct
Second is incorrect
3+1 is 4
4≤-4x
Did I get everything wrong
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.
These interval notations don’t even make sense like 3 says 0 is the biggest so why does it go to 4
5x-3<7 5x-3>-7
One sec
Left side is -∞ and right side is +∞
Graph looks like this
We don't need 0 cause it's not solution
It says 0 is biggest so it shouldn’t go past 0
Who says
That’s what it says
What’s even the point of <0 then
nah
they dont say x<0
They say graph<0
so graph is less than zero when it's from -3 to 4
We only use roots as dots in graph
So when am I suppose to use the negative infinite and positive infinite signs
When u need + ones
Left side is -∞ and right side is +∞
But we don't need +
Cause we need -
Cause graph<0
And the module you did wrong, this is the right way
Goddamn, you need to study polynomial inequalities...
why the judgement?
Cause he messed up everywhere
you have no idea about their situation. judgement is not appreciated on this server
Bro what a hell
He made a lot of mistakes, so he needed theory and practice more, isn't it obvious?
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where did i make a mistake?
im trying to derive arctan'(x) by using the derivative of inverse function formula
whats the formula?
its written on the left there
next to the 1/tan'(arctanx)
because of the chain rule
and im multiple with arctan'(x) not arctanx
isnt that what i put? 1/tan'(arctanx)
yes and thats it
no chain rule
tan'(arctanx) = sec^2(arctanx)
its different from (tan(arctanx))'
maybe thats why youre confused
is it?
it is
you would use the chain rule there
not there
how would you write it with d/dx
(tan(arctanx))' is d/dx (tan(arctanx))
how would you do tan'(arctanx)
because i dont see any way to do it
and also i simplified tan^2(arctanx) to x^2 since its equal to (tan(arctanx))^2
maybe $\frac{d}{dx}(\tan x) \circ \arctan(x)$
LF
where are you doing tan^2(arctanx)?
in the second last line
oh sorry yeah thats good
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Article containing written solution to this problem:
https://medium.com/nice-math-problems/find-all-positive-integer-solutions-f0e69909e73a
More China Girls Math Olympiad problems can be found here:
https://artofproblemsolving.com/community/c3287_china_girls_math_olympiad
Outtro: Walking Home by Alex-Productions | https://onsound.eu/
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why can the numerator be equal to the power?
just watching the video, can someone explain why?
also, why does he divide by factors of 2?
@formal needle Has your question been resolved?
<@&286206848099549185>
Screenshot it outline the proof. Not many people are going to watch a whole video to help
i literally did
its here
You need to explain the assumptions
^
no i just want to know like whats the rule that lets you set the numerator equal to the power of the denominator
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You can't pull that stuff involving x out of the integral
José
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x and t are related
you can't treat x as a constant
don't think ibp ends well here
for ibp you'd also want the derivative of the other component to be get simpler. can't just focus on part of it.
for this question, if first approach this with partial fraction decomposition
takes practice to see what might help, how you should approach certain problems.
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what is the solution set of sqrt root 4x+21 =x?
i got -3 and 7 but -3 isnt a solution, how?
yea thats what i did, but it doesnt make sense to me
why is that the case?
why is what the case
that -3 doesnt work?
because i formed a quadratic equation
and negative 3 should be an answer
immediately you can see that -3 is wrong because the square root can only output positive values
but is there any other way of seeing it?
performing the algebra correctly
i did tho, no?
7 is right
yup
Okay so what did you get after that?
4x+21=x^2
sqrt(4(7)+21) = sqrt(28 +21) = sqrt49 = 7
|4x+21|=x^2 *
why that sign?
I have it backwards
apologies
sqrt(x^2)
=|x|
not = x
not the way I written it
can't you also do it =±x
When you square both sides you pick up an extra solution because
im aware
if the left side was negative
then now it is positive
and you gain that solution
but the left side never could have been negative
no
that means absolute value
Okay I was making that symbol because earlier I thought your confusion came from that you did not realize that sqrt(x^2)=|x| and you had thought sqrt(x^2)=x
do you not see the sqrt that I typed
yea
So what is confusing you then
the issue is that there is a context of the domain you're working in floating in the background that's easy to forget.
you have sqrt(4x + 21) = x. the square root only outputs (by definition) nonnegative numbers, so in order for x to be equal to sqrt(something), it's necessary that x >= 0.
now, you square both sides and get the parabola x^2 - 4x - 21 = 0. as a function from the real numbers to the real numbers, the parabola x^2 - 4x - 21 intersects the x-axis in two places: x = -3 and x = 7. however, remember, you're only looking for solutions that are greater than or equal to 0. so really, you're looking for where the graph of the parabola intersects the line {(x,0) : x >= 0}
@royal steppe Has your question been resolved?
wait so square roots only output positive numbers?
but what about smth like square root of 4
its + - 2
yeah. you're pointing out that both 2^2 = 4 and (-2)^2 = 4. but sqrt(x) as a function is defined to output the nonnegative square root of x.
the reason for this is kind of clear. say you have 4, and you want to take the square root. you can only return one number (because functions only return one thing). thus, you have to pick one of the two options. the convention is to pick the one that's >= 0
that's why, as austin was saying, sqrt(x^2) = |x|. because sqrt(x^2) is the nonnegative number y such that y^2 = x^2. this number y must be equal to |x| (because its either x or -x, and you have to pick the one thats nonnegative. this is what |x| is defined to be)
its kind of obnoxious when you first learn this, since there's all these different meanings of square roots
basicallly $\sqrt{4}=2$ but $x^2=4 \Rightarrow \sqrt{x}=\pm2$
Prime Minister
hell yeah math
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Given A = [ 7 5 ] and B = [ 3 5 ], Find a matrix Q such that BQ = 2A
[ 8 9 ] [ 1 2 ]
The answer is supposed to be [ -52 -70 ]
[ 34 44 ]
but im getting [ -52 -70 ]
[ 64 68 ]
can you show your work?
uh i don't have a phone atm
but i can type it out
so
first i decided to find 2A
which gives us the 2x2 matrix [ 14 10 ]
[ 16 18 ]
ok now you have BQ=2A, how do you solve for Q?
and that would be?
which was [ 2 -5 ]
[ -1 3 ]
but B^-1 * 2A gives me the answer i obtained above
which apparently is incorrect
I think the big numbers are messing you up a little just try doing B^(-1)*A
instead of B^(-1)*2A
I assuming you know how to matrix multiplication?
yes
i hope so
i could be wrong
do you think you can try to B^(-1)*A? If so, can you try to show your work :)
why don't i show u the what i did to obtain the product of B^-1 times 2A here?
sure that works
do you have it written down?
i multiplied 1 with 14, instead of multiplying 14 with negative 1
always check your work!
the thing is
my handwriting on the paper was a bit too messy
so i interpreted it as positive 1 the whole time
it was when i was typing out the matrix products i realized the error
lol
because you double checked always do that on tests :) especially when you got all those numbers
and trust me 3x3 and 4x4s only get way crazier with multiplication
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good luck!
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with this, we know that the triangle ABD is equivalent to the triangle EFD
how
similar or equal
the same occurs with the triangles CBD and EBF
equivalent
how
they have the same ratio
so EF= 12???
He means same ratio not same length
if theres a line crossing a triangle 90° in relation to a face, it creates an equivalent triangle
so they are similar
like if height is 12
base 2
then the other one would be
18 and 3
??
pls continue
exactly
hello??
oh man it’s harder than i thought
ye
i apologize as i think i can’t help you any further than this
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i need help with this problem
im stuck i dont even know where to start
do you know calculus
find derivative of this function first
4 equations will come up
2 for extremum and 2 for normal value of polynomial
Lol
like help me solve it i dont understand this terminology
Look at x=-2 p has the value of 3 so a.2³+b.2²+c.2+d =3
Similarly for the other point
Also a
If is not Turning point then u can't solve it
Turning in the sense it's minima right?
i dont understand what you're saying im sorry
Gand maara
but there is a solution to this i just dont know how to get it
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do you guys have pascals triangle for high exponents
like 12-20
Probly write a code or smth to generate mate!
Or you could calculate nCk
By hand I meant that ^
you could use approximations
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Let ( ABC ) be a triangle with ( AB \neq AC ), let ( I ) be its incenter, and ( \gamma ) its inscribed circle, and ( D ) the midpoint of ( BC ). The tangent to ( \gamma ) through ( D ) different from ( BC ) touches ( \gamma ) at ( E ). Prove that ( AE ) and ( DI ) are parallel.
Alex
any idea how to start?
Well
If the tangent is at D
How is it supposed to again touch the circle at E
I’m struggling to start with the problem. I understand that I need to prove that lines AE and DI are parallel, but I’m not sure how to use the fact that D is the midpoint of BC and how this relates to the tangent to the incircle
<@&286206848099549185> any hint?
@clear flint Has your question been resolved?
feel free to ping me
@clear flint Has your question been resolved?
@clear flint Has your question been resolved?
@clear flint Has your question been resolved?
@clear flint Has your question been resolved?
Do you know projective geometry?
If you do, use this lemma:
If ABCD is a harmonic quadrilateral inscribed of (O) and l is the tangent line at D, the intersections of the tangents at A,B,C to (O) and l form a harmonic bundle
After that it’s easy
@clear flint
that mean that the cross ratio of the four points is -1 right? if I apply this to our problem, I should look at the tangents to the circle at points A, B, C, and the tangent line at D. But I’m not quite sure how to construct this harmonic bundle from the tangents
ok i got it, thx @supple mural
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hi i need help asap
Is it sin³(nx)
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I need help with multivariable Taylor series specifically with sin(x+y)
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Find two polynomials p(x) and q(x) that satisfies the given condition and such that p(x) -> +Infinity and q(x) -> +Infinity as x -> +Infinity
hecker
$$
\[ \lim_{x\to\infty} [p(x) - q(x)] = 3\]
$$
```Compilation error:```! LaTeX Error: Bad math environment delimiter.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.53 \[
\lim_{x\to\infty} [p(x) - q(x)] = 3\]
Your command was ignored.
Type I <command> <return> to replace it with another command,
or <return> to continue without it.```
There were 3 similar questions before and I solved them
But I don't understand how a polynomial that goes to infinity subtracted by a polynomial of same behaviour can equal 3
maybe all is need is p=q+3
Ohh yes that works, didnt think of that
I am having some trouble with limits you see
But thanks
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👍
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dont know how im supposed to get the equation of the quadratic.
Well based on the fact that the turning point is in the middle of roots
another root = 4 + (4 - (-2))
= 10
With the formulas of
Product of roots = c/a
Sum of roots = -b/a
hecker
Now you have to find out what a is such that the turning point is (4, 24)
Based on some eye balling in desmos I can say that a= -2/3
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If you have a line defined by:
5x - 3y - 8z + 42 = 0
x - 9y +4z +28 = 0
How do you find the numbers for the direction vector of this line?
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36/64
Why do you want to square root
Yh
Then why square root
no, you can't do square root
I know answer is 9/16
U can't square root
With divison 2
You can simplify in different ways, depending what do you want to achieve
U have to divide by same number
Im asking if i can do square root
Yeah u cant
To simplfy
Cuz 1/4 isn't equal to 1/2
ok but if i see a big numbers
simplification is the process of transforming what you have while preserving the value
Can i do something else than divison 2
Square roots has nothing to do with common factors
square root does not preserve the value
U can divide by any number
Just divide or multiply
The proportion when u divide both, numerator and denominator are the same when u divide with the same number
This doesn’t happen when u apply square root to two different numbers
Like 1/2 isn't equal to 1/4
But yes u can divide by numbers that aren't 2
So 3/6 can become 1/2 (divide top and bottom by 3)
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how would I find the number of triplets satisfying 2^x+2^y+2^z=2336
can I have. a hint
is there any standard way to solve such dopiantine equations?
,w prime factrorise 2336
ok, so I'm guessing I have to use the prime factorisation somewhere
but where
<@&286206848099549185>
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Lets say I have a polar curve:
$r=1-2sin(3\theta)$
rainy
How would you know that it corresponds with D
I know 1-2sin(theta) has this kind of shape
i just dont know how to handle the 3 theta

- it has two have 3 "petals" (due to 3 theta)
- substituting 0 should yield 1
so based upon your 1), my only options are A & D
and then subsituting should give me D
lets see
ye
yes
Ah so, subsituting 0 as an angle (theta) gives back where r is at that angle
okkkkkkk
i get it
thx
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Is this a valid solution to the problem?
Looks valid to me
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right?
Is y(0) = C given to you anywhere? with exception of that, everything else seems fine to me 
@night rapids Has your question been resolved?
yes
do you have the original question in picture form? seems strange how there's reference to the integration constant in the question 
Consider the two differential equations
y′(x) = 4py(x)x (1)
y′(x) = y(x)2. (2)
(a) For all C > 0, find a continuous function y : [0, ∞) → [0, ∞)
with y(0) = C which is differentiable on (0, ∞) and satisfies the diffe-
rential equation (1) here
@brittle beacon
Not entirely sure whether that C in the question is supposed to match up with the integration constant you find 
yeah same
Think that the final answer you get should be in terms of that C
i am not sure whether it is the same C
bit odd to not call it C_1 or somethingh then
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But like say when you get to like the point $2\sqrt{y} = 2x^2 + c$ (little $c$) then you make use of the fact that $y(0) = C$ to get that $2\sqrt{C} = c$
@brittle beacon
.reopen
✅
yeah it doesnt change too much but i also thought of that
At which point $\sqrt{y} = x^2 + \sqrt{C}$ and stuff
@brittle beacon
Yep
of course you can simplify that down by cancelling down the 2's
"Consider the two differential equations
y′(x) = 4py(x)x (1)
y′(x) = y(x)2. (2)
(a) For all C > 0, find a continuous function y : [0, ∞) → [0, ∞)
with y(0) = C that is differentiable on (0, ∞) and satisfies the differential equation (1) here."
Do you think in this i have to prove it it continuous and differentiable?
I mean I doubt you do, but showing it satisfying the differential equation pretty much does all three at the same time (any differentiable function must be continuous!)
Like it should be easy to see that $y = \pqty{x^2 + \sqrt{C}}^2$ is differentiable of course
@brittle beacon
well you're given that C > 0 already, in the question ("For all C > 0...")
Which is a good thing because you can take the square root of it 
i read it as for C>0 (which in turn you have to prove it is)
I more read it that they give you that C is (strictly) greater than zero, which you can take freely, and you then work with that
ok nice ill just hope that is what it is
I do 
Yep pretty sure that they probably intend it that way (it's the way that is most likely
)
b)
"Find two different continuous functions y : [0, ∞) → [0, ∞) with y(0) = 0 that are differentiable on (0, ∞) and satisfy the differential equation (1) here.
(c) For all C > 0, find a number K > 0 and a continuous function y : [0, K) → [0, ∞) with y(0) = C that is differentiable on (0, K) and satisfies the differential equation (2) here. For the given C, what is the largest possible value of K?"
anyone please help me with this question-Consider that a, b, c, d are positive real numbers satisfying (a + c)(b + d) = ac + bd.
Find the smallest possible value of S=a/b+b/c+c/d+d/a
!occupied
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The differential equation $y'(x) = 4 \sqrt{ y(x)} \cdot x$?
@brittle beacon
So like that? 
// mav
yes
Wait for part b or for part c?
b)
"Find two different continuous functions y : [0, ∞) → [0, ∞) with y(0) = 0 that are differentiable on (0, ∞) and satisfy the differential equation (1) here.
with the equation we have just shown with TeXit ab ove
b
y' = dy/dx
Then we've basically done that already
all the stuff above where we got that y = (x^2 + sqrt{C})^2
yh
now what
how do i find two constants
when C = 0 ?
since y(0)=0
x=0 , y=0
Basically pick two different [strictly] positive C's really, say C = 4 and C = 9 or whatever
Then they're different functions but as per what you found must satisfy the DE 
isnt that a bit too easy 
Well I mean it doesn't need to be that challenging, as it follows from all the hard work you did before 
but how do i just pick C = 4
C has to be 0, no?
Oh yea, didn't read
they do say y(0) = 0, nvm
Well I mean in that case, the one you found satisfies the DE, but also rather trivially the constant function y = 0 also meets all the requirements stated too
@night rapids Has your question been resolved?
how is y=0 a value of C
and none of the are above 0
nvm it doesnt have to be thatg here
The function that just outputs zero, is what I meant haha
what
i guess y=0 would be correct
@night rapids Has your question been resolved?
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how would you theoretically do these questions with "Guess and check" method
for the first one
oh
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suppose R is (3,5) and S is (8,-3). Find each point on the line through R and S that is three times as far from R as it is from S.
i finished finding hte first solution
which was 6.75,-1
however idk how i should find the second point
i have somehwat of an idea
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hello i was trying to solve a question and i wonder if i got the integral correct: two identical conical piles of sand with a height of 1m and radius of 1m overlap each other. the distance between the two vertices is also 1m. find the volume of the combined pile.
i just set up this integral $2\int_{-1}^{\frac{1}{2}}\int_{-\sqrt{1-x^{2}}}^{\sqrt{1-x^{2}}}\left(-\sqrt{x^{2}+y^{2}}+1\right)dydx$
Jill ♡
@versed obsidian Has your question been resolved?
<@&286206848099549185>
I came back now, but how am i supposed to write it? y(0) is the function that just gets 0
ik you cant write here, but noone was helping so i just did it anyways
this isnt your channel anymore...
(You’ll need to open a new channel but tl;dr just have y(x) = 0)
use another one
$$ V = \iint\limits_{D} \left(1 - \frac{1}{h} \sqrt{x^2 + y^2}\right)^2 - \left(1 - \frac{1}{h} \sqrt{(x-1)^2 + y^2}\right)^2 , dx , dy $$
// mav
could that be an answer?
i dont understand what the 1/h is for
i guess but the cones are identical in volume so we dont need the 2nd root
idk, i am not really sure on this one tbh
but i think you're in the right direction at least
what class are you doing?
none i found this online
the cones intersect each other on a straight line
so i just assumed i should decrease the integral boundaries
<@&286206848099549185>
@versed obsidian Has your question been resolved?
do u have a pciture
i just plotted the thing
they intersect at x = 1/2
@versed obsidian Has your question been resolved?
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What am I doing wrong here?
-
I found the circumference of the wheel doing $r=0.5(20)$ and then $c=2 \pi \cdot 10$.
-
Then I took the number of revolutions per minute and multiplied it by the circumfrence of the wheel (in inches) which should've gave me the inch/min. $(2 \pi \cdot 10)195=12252.211349$
Matt
But for some reason thats wrong, not sure why as multiplying the circumfrence by the amount of revolutions/min should give me inch/min
at least i thought so lol
@mystic saffron Has your question been resolved?
Think about how a standard bicycle works. You pedal, which moves the front sprocket attached to the pedals. The front sprocket moving causes the chain to move. The chain is attached to the front sprocket and the rear sprocket, so the chain moves the rear sprocket. The rear wheel is attached to the rear sprocket, so the rear sprocket moves the rear wheel.
If the cyclist pedals at 195 RPM on the front sprocket with a 6 inch radius, how far in inches does that move the chain along the front sprocket per minute?
@mystic saffron
Then, the chain will also move that far along the rear sprocket. That sprocket has a 4 inch radius, so how many RPM is the rear sprocket doing?
Then, the rear wheel, which has a radius of 20 inches will move that many RPM, so how far does it go in a minute?
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the answer to this is apparently vertical strech by a factor of 3 (i agree with) and a vertical shift 3 units up????
should it not be horizontal comp by a factor of 1/8?
$8=2^3\implies 8x^3=2^3\cdot x^3$
Try using some of the log laws to separate it
PajamaMamaLlama
yeah I get this
but if it were a vertical shift
it would have to be
$(x^2 \pm something)$
$log_28x = log_28 + log_2x$
This is why
^
Do you mean vertical shift up 3?
Vertical shift right isn’t possible
Yep!
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Np
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so when it says distance from origin, surely it means shortest distance right?
because a plane would have infinite number of distances from origin?
yes that's what that would mean 
well i dont really understand how this works tho
what does root 14 even mean
hmm ig it doesnt have to mean anything, its just for finding equation
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I mean I wouldn't consider it easy
You could try Cramer's rule(very tedious) and the normal way to find the matrix determinant and compare those
But I don't know if there is an easy way to check
Just use any online calculator that supports determinants like wolfram
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i need help
when this is asked do i just have to plug in 4 years where the t is at?
because when i plug that in i get 500^125./e^109/e
yea find A(4) which is the amount of radioactive lead remaining after 4 years
@merry grotto
and round to the nearest integer
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How do I make $k^2(k+1)^2+4k+4/4$ be $(k+1)^2 (k+2)^2/4$
ICANTCOMEUPWITHANAME
Is it allowed to add k² to the 4k + 4 so things would be much more simpler? Even though k² is attached to (k+1)²
$\frac{k^2(k+1)^2+4k+4}{4}$ be $\frac{(k+1)^2 (k+2)^2}{4}$
Wither
I don’t think u can, cause it’s stick with the first expression
Priority to multiplication
Might have a made the induction wrong
Maybe
@tough plinth Has your question been resolved?
There's somthing wrong with this induction and Idk what
,rotate
What are you trying to solve?
I cant make that expression from the left equal to the right
Ahh yes
Prove that the left side is equal to the right
The k squared on the left is connected to the (k + 1)^2
So it’s actually (k^2 + 4)(k + 1)^2 / 4 being correct
Wait no
I don’t think you can simplify this
Not really
;-;
Yes
$(k + 1)(k^2(k + 1) + 4)$
ICANTCOMEUPWITHANAME
Yes
This is equal to
The left side
The right and left are not equal
It is though
Reference to those at step 1 , I used 3 examples
And it all came out equal
1, 9, and 36
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question: find the sum of all possible 4 digit numbers that can be made using the digits 2,3,4 and 5 exactly once. I found a way to approach this problem but i think there's a flaw in it. Break the 4 digit number in the following manner: 10³×a +10²×b +10¹×c +d. 'a' can take any of the four values (2,3,4,5) and that would repeat 3! times. Similarly, for b, c and d. So the answer would be 10³×(3! ×14)+ 10²×(3! ×14)+ 10¹×(3! ×14)+ 10⁰×(3! ×14). But i suppose the cases would be repeated. For example, consider the number 2345. It would appear once when a=2, once when b=3, once when c=4 and once when d=5, which means it has been repeated 4 times.
wym?
yeah of course it would appear 4 times
you're counting each of its four places separately
the thousands, hundreds, tens and ones
but the answer is correct
2345+2354+2435+2453+2543+2534+3245+3254+3425+3452+3524+3542+4325+4352+4235+4253+4532+4523+5342+5324+5432+5423+5234+5243 = 93324= 10³×(3! ×14)+ 10²×(3! ×14)+ 10¹×(3! ×14)+ 10⁰×(3! ×14)
@mystic saffron Has your question been resolved?
<@&286206848099549185>
<@&286206848099549185>
the answer is 93 thousand 300 and 24
i know that
@mystic saffron Has your question been resolved?
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I need help solving this equation system, I see that it is a vandermonde determinant but I'm not sure if that's helpful or not
@sharp bay Has your question been resolved?
@sharp bay Has your question been resolved?
can someone help me?...
@sharp bay Has your question been resolved?
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hint: when is cos(theta)=1 in 0≤theta≤2π
in the first and 4th quadrant?
not really, it's just exactly when theta=0 or 2pi
Cheers!
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is it possible/allowed to
I mean it does have the required form, though it is much more pain to do it with lopital's
You may want to multiply and divide $\sqrt{x^2 + 1} - x$ by its conjugate
@brittle beacon
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,w integrate (2x+1)/(x^2-1)
EMINEM
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Need help solving this solved the quadratic but idk what to do with the modul bit
|x|+7 is always >7 for all real x
so you need to only consider the num
the inequality reduces to x^2-5x+6<=0
can you factorize the quadratic?
Mmm so |x|+7 >0?
yes
Can it be equal?
If I square it would it work?
so, |x|+7>=7 for all real x
what would you square?
This
why would you want to square it?
Ok so what would i do?
just focus on this
you should have something like (x-2)(x-3)<=0
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what can you say about the order of Q
wdym by that
this is the solution, im curious as to why the inverse R is on the right of I on the rhs instead of being to the left of the rhs
because R is on the right of Q on the LHS
yes
and if B was a 2x1 matrix there would be no solution?
is this scenario
if a matrix isnt square, it doesnt have a 2 sided inverse
what are X and A in that case?
2x2?
well you cant even multiply the matricies X and A in that case
yeah
so if it was ABC = X, where they are all 2x2 matrices
A'ABC = A'X
A'AB'BC = B'A'X?
if i were solving for c?
or would it be
A'AB'BC = A'B'X
this is the correct answer, but slightly wrong process
A'ABC = A'X yes
but it's B'A'ABC = B'A'X
B' needs to go to the left of A'
why?
because B'A'ABC = B'(A'A)BX = B'(I)BC = B'BC = C
if you prefer to think about matricies as linear transformations
then it's because we first apply C, then apply B, then apply A to get the matrix ABC
to "undo" this
ahh
we must apply the inverse linear transformations backwards
so A' comes first, then B' comes after
in order to get back to C
in this solution why do they not start from R
yeah it's the same as for function composition
because Q is in the middle, so it doesn't really matter which we do first
you get the same result in the end either way
[f o g o h]^-1 = h^-1 o g^-1 o f^-1
👍
anyone know much about physics, specifically how to find critical angles and refractive indices
Which grade is that in if I may ask?
not in usa but i am 16
for refractive indicies, if you know the speed of light in a material, then divide c by that speed to get the refractive index of the material
the question is a weird one
show?
to answer about the critical angle
the critical angle is the angle of incidence such that the resulting angle of refraction is 90 degrees
any angle of incidence greater than the critical angle will result in total internal reflection
part iv, part iii is backround info i guess
i know the basics like how to find crit angle and all that
but this question is a weird one
what's your issue with it?
if you can calculate critical angle, then this is pretty straightfowards
show pls
Its asking for the critical angle of the core/cladding boundary
yes, it is
but we only know the refractive index of air to core and air to cladding
why is that an issue?
because we need the critical angle from core to cladding im pretty sure
yes, but we have the refractive indicies
how would i use them to find refractive index or critical angle of the core / cladding boundary
refractive index = 1/sin C
btw
i'm a bit confused
the refractive indicies of the two materials are all you need
what else is there to calculate?
theres no 3rd material
as for critical angle, you said that you know how to calculate it i think?
so it's the same as always if you've done it before
how would you do it? im unsure as to which figure to use
yes

