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Calculus1 6 Online
OpenStudy (anonymous):

Can someone please help me integrate these problems attached?

zepdrix (zepdrix):

Cinnnnn! Where's the attachment lady? c:

OpenStudy (anonymous):

sorry lol

OpenStudy (anonymous):

can you see it

OpenStudy (anonymous):

there is an s \[\int\limits_{-14}^{1}s \left| 4-s^2 \right|\]

zepdrix (zepdrix):

Oh oh oh, didn't see that >.< ty

OpenStudy (anonymous):

sorry 49 still typo

zepdrix (zepdrix):

\[\Large\rm \int\limits\limits_{-14}^1s\left|49-s^2\right|ds\]

OpenStudy (anonymous):

correct

zepdrix (zepdrix):

Lemme see if this makes sense.... \[\Large\rm \left|49-s^2\right|=\left|(7-s)(7+s)\right|\] \[\Large\rm =\cases{-(7-s)(7+s), &s < -7\\ \rm \quad(7-s)(7+s), &-7 < s < 7}\]Do you understand what I'm doing with the pieces here? Ahhh I can't.... words.... blah

OpenStudy (anonymous):

yes you broke it down because it is an absolute value

zepdrix (zepdrix):

So we have to rewrite our integral as the sum of two integrals. We need to break up the boundary at -7

OpenStudy (anonymous):

ok

OpenStudy (anonymous):

would the bounds be -14 to -7 and -7 to 1

zepdrix (zepdrix):

Yes those bounds sound correct c:

OpenStudy (anonymous):

ok and then we integrate

zepdrix (zepdrix):

\[\Large\rm \int\limits\limits_{-14}^{-7}-s(49-s^2)ds+\int\limits_{-7}^1 s(49-s^2)ds\]So I wrote these back as squares because we'll want to apply a substitution. Easier to do so without factoring it. The factoring was just to see where the bad spots were in our absolute.

OpenStudy (anonymous):

ok I see question how did you know to split it at -7?

zepdrix (zepdrix):

Oh boy.. how to put this into words.. ummm

zepdrix (zepdrix):

|dw:1408507574855:dw|If you look at the function y=x,

OpenStudy (anonymous):

uhhhm

zepdrix (zepdrix):

|dw:1408507610842:dw|And take the absolute value of x, what you're really doing is, applying a negative to the x when x is negative. That's what flips the branch up to being positive on the left side. That's what the absolute function does, it applies a negative if we would be negative, changing it to positive in the end.

zepdrix (zepdrix):

So when we have a factor of |7+s|, when we're below -7, the inside is negative, so the absolute function tells us to apply a negative

zepdrix (zepdrix):

Bahh this is the worst explanation >.<

zepdrix (zepdrix):

lol

OpenStudy (anonymous):

Yes I understand that, but in this equation would you just look for where the function became negative and that would be your bound

OpenStudy (anonymous):

no it was good

zepdrix (zepdrix):

|dw:1408507831863:dw|

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