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OpenStudy (whpalmer4):
There's nothing there to solve. Do you mean expand it?
OpenStudy (anonymous):
yes
OpenStudy (anonymous):
mmm loooks hard
OpenStudy (anonymous):
lke multiply its square
OpenStudy (anonymous):
dont know if i can do it
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OpenStudy (anonymous):
helpppppppp
OpenStudy (anonymous):
multiply its square
OpenStudy (anonymous):
is it (x-x^2)(X-X^2)
OpenStudy (anonymous):
is it x^4-2x^3+x^2
OpenStudy (whpalmer4):
\[(x-x^2)(x-x^2) = x(x-x^2) - x^2(x-x^2)\]by the distributive property. Now do that again and collect like terms.
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OpenStudy (anonymous):
\[\left( a-b \right)^2=a^2+b^2-2ab\]
\[\left( x^2 \right)^2=\left( x \right)^{2*2}=x ^{4}\]
OpenStudy (anonymous):
Are you familiar with the acronym FOIL? First, Outside, Inside, Last?
OpenStudy (whpalmer4):
FOIL is a bad crutch — useless as soon as you start multiplying anything other than binomials. Better to think of it as distributive property, repeatedly applied.
OpenStudy (whpalmer4):
\[ x^4-2x^3+x^2\] is correct, good job!
OpenStudy (anonymous):
i reather distribute
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OpenStudy (anonymous):
@whpalmer4 Good point.
OpenStudy (anonymous):
wait now
OpenStudy (anonymous):
antiderive that
OpenStudy (anonymous):
pls
OpenStudy (whpalmer4):
Now you want to integrate it?
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OpenStudy (anonymous):
anti
OpenStudy (whpalmer4):
the antiderivative is the integral. do you want the integral, or the derivative?
OpenStudy (anonymous):
1/5x^5-2x^4+1/3x^3 what i got
OpenStudy (anonymous):
n yes integral
OpenStudy (whpalmer4):
Well, this is an indefinite integral, so you forgot the arbitrary constant of integration. Not optional!
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OpenStudy (anonymous):
pi interal from 0 to 1 the function
OpenStudy (anonymous):
antiderrive the function
OpenStudy (whpalmer4):
But we'll pretend you had it there, and check answer by taking derivative:
\[\frac{d}{dx}[\frac{1}5 x^5-2x^4+\frac{1}{3}x^3+C] = 5*\frac{1}{5}x^{5-1}-4*2x^{4-1}+3*\frac{1}{3}x^{3-1}+0 \]\[= x^4-8x^3+x^2\]That's not correct...
OpenStudy (anonymous):
you know to much swag. just checking though
OpenStudy (anonymous):
umm the function is x^4-2x^3+x^2. sorry if i sound rude
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OpenStudy (anonymous):
i want to antiderrive
OpenStudy (whpalmer4):
\[\int x^4-2x^3+x^2 \,dx = \frac{1}{4+1}x^{4+1}-\frac{2}{3+1}x^{3+1} + \frac{1}{2+1}x^{2+1} + C \]\[=\frac{1}{5}x^5-\frac{1}{2}x^4+\frac{1}{3}x^3+C\]
Yes, and I was pointing out that you made a mistake, because when we take the derivative of what we get when we take the antiderivative, we should end up with the same thing!
OpenStudy (anonymous):
so (1/5)x^5-2x^4+(1/3)x^3 should
OpenStudy (anonymous):
Break it up into separate integrals and take the constants outside the integrands.
OpenStudy (anonymous):
ohhh ok
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OpenStudy (anonymous):
ok1/2
OpenStudy (anonymous):
well then that was rathe silly of me. all this time lol
OpenStudy (whpalmer4):
When in doubt, check your work. When not in doubt, check it anyhow :-)
OpenStudy (anonymous):
ok now multiply all of that by pi and plug 1 into x
OpenStudy (anonymous):
go i race u
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OpenStudy (whpalmer4):
now hold on, you're evaluating a definite integral now? what are the limits?
OpenStudy (anonymous):
yup
OpenStudy (anonymous):
0 to 1
OpenStudy (anonymous):
lol
OpenStudy (whpalmer4):
\[\frac{\pi}{30}\]
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OpenStudy (anonymous):
rady
OpenStudy (anonymous):
what
OpenStudy (anonymous):
how what when where
OpenStudy (whpalmer4):
You said evaluate it from x = 0 to x = 1 and multiply by 30. I did. That's my answer.
OpenStudy (anonymous):
u go the right answer
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OpenStudy (whpalmer4):
of course I did! :-)
OpenStudy (anonymous):
ok dont u need a comon denominator for the number in ()
OpenStudy (anonymous):
30
OpenStudy (anonymous):
lol just did the math. damm ur fast
OpenStudy (anonymous):
i got it
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OpenStudy (anonymous):
im also stuck on another problem which i have no idea how to do start or end
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OpenStudy (anonymous):
\[\pi \int\limits_{0}^{1}(\tan(\pi/4)x)^2dx\]
OpenStudy (anonymous):
so how do we square the tan????????
OpenStudy (whpalmer4):
Isn't that supposed to be \[\pi \int_0^1 (\tan(\frac{\pi}{4}x))^2\,dx\]
OpenStudy (anonymous):
yea
OpenStudy (whpalmer4):
oh, probably take \[u = \frac{\pi}{4}x\] as the substitution, and rewrite \(\tan^2 u\) as \(\sec^2u -1\)
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OpenStudy (anonymous):
ok
OpenStudy (whpalmer4):
give it a try, I'll stick around and help if needed
OpenStudy (anonymous):
ok
OpenStudy (anonymous):
is sec^2u-1 the antiderrivative or just rewritten?
OpenStudy (anonymous):
???
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OpenStudy (whpalmer4):
Yes?
OpenStudy (anonymous):
rewritten?
OpenStudy (whpalmer4):
I'm a little unclear on the question you are asking me here :-)
OpenStudy (anonymous):
is sec^2u-1 the antiderrivative or just rewritten?
OpenStudy (anonymous):
could you do it im kinda tired.not to be mean or anything :)
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OpenStudy (anonymous):
it is the identity you use to find the anti derivative since the anti derivative of \(\sec^2(x)\) is known to be \(\tan(x)\) and the anti derivative of \(-1\) is \(-x\)
OpenStudy (anonymous):
satellite meet whpalmer, whpalmer meet satellite . you guys are smart lol
OpenStudy (anonymous):
ok
OpenStudy (anonymous):
if it is \(\tan^2(\frac{\pi}{4}x)\) make the substitution
\[u=\frac{\pi}{4}x\] and change the limits of integration while you are at it