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Mathematics 10 Online
OpenStudy (anonymous):

use the fundamental theorem of calculus to evaluate this equation

OpenStudy (anonymous):

\[\int\limits_{0}^{2}(3-5x^4)dx\]

OpenStudy (freckles):

so what?!? You actually get to use calculus to find the area or net area now?

OpenStudy (freckles):

lets talk about antiderivatives then

OpenStudy (freckles):

( what goes here)'=3

OpenStudy (freckles):

what can you take the derivative of that will give you 3?

OpenStudy (anonymous):

hi again freckles, not exactly sure what to do here

OpenStudy (freckles):

well this is the short cut way to what you have been doing

OpenStudy (anonymous):

thank god

OpenStudy (freckles):

we actually did this one day together on a problem

OpenStudy (freckles):

like we had \[\int\limits_{0}^{1}(x^2+1)dx=(\frac{x^{3}}{3}+x)|_0^1=(\frac{1^3}{3}+1)-(\frac{0^3}{3}+0) \\ =\frac{1}{3}+1=\frac{1}{3}+\frac{3}{3}=\frac{4}{3}\] remember this I didn't do the last line because I was leaving the simplifying to you

OpenStudy (freckles):

like just like we found the antiderivative of (x^2+1) in that example we need to find the antiderivative of 3-5x^4

OpenStudy (freckles):

Let c and d be some constant number. The antiderivative of c is cx+d since (cx+d)'=(cx)'+(d)'=c(x)'+0=c(1)+0=c+0=c. That is \[\int\limits_{}^{}c dx=cx+d\] when we have definite integrals like: \[\int\limits_{a}^{b}c dx=cx|_a^b=c(b-a)\] we don't need to put the constant of integration (the one I called d above in; you can put it will just get canceled out)

OpenStudy (anonymous):

so, 3x - x^5 is the antiderivative

OpenStudy (freckles):

wow yep that is right

OpenStudy (freckles):

so you have: \[\int\limits_{0}^{2}(3-5x^4) dx =(3x-x^5)|_0^2\]

OpenStudy (anonymous):

now I take the anti of F(1) minus the anti of F(0)

OpenStudy (anonymous):

2, not 1

OpenStudy (freckles):

the next step is to evaluate that antiderivative expression at the upper limit 2 and then put a minus and then evaluate the antiderivative expression at the lower limit 0

OpenStudy (freckles):

and yes

OpenStudy (freckles):

well the anti if the F since the integrand was the f where you know F'=f

OpenStudy (freckles):

but I think I got what you are saying

OpenStudy (anonymous):

ok, here goes

OpenStudy (freckles):

well the ant is the F*

OpenStudy (freckles):

ok I'm ready when you are :p

OpenStudy (anonymous):

came up with -58

OpenStudy (freckles):

hmm how did you get that exactly you did this: \[\int\limits\limits_{0}^{2}(3-5x^4) dx =(3x-x^5)|_0^2 \\ =(3 \cdot 2-2^5)-(3 \cdot 0 -0^5)\]

OpenStudy (anonymous):

oops, it's actually

OpenStudy (anonymous):

-26

OpenStudy (freckles):

sounds beautiful that is actually a net area We know this because |dw:1429484706053:dw|

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