I am integrating by parts. I do not know what let u and v be. I am also stuck on the radical.

e^{sqre rt} 3s+9 ds

I want to let u = 3s+9 and v = e^rt x

can it be done or am i just lost?

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- Feb 25th 2009, 12:01 PMswensonm[SOLVED] Integration
I am integrating by parts. I do not know what let u and v be. I am also stuck on the radical.

e^{sqre rt} 3s+9 ds

I want to let u = 3s+9 and v = e^rt x

can it be done or am i just lost? - Feb 25th 2009, 02:02 PMskeeter
$\displaystyle \int e^{\sqrt{3s+9}} \, ds

$

$\displaystyle t = \sqrt{3s+9}$

$\displaystyle dt = \frac{3}{2\sqrt{3s+9}} \, ds = \frac{3}{2t} \, ds$

$\displaystyle ds = \frac{2t}{3} \, dt$

$\displaystyle \int e^t \cdot \frac{2t}{3} \, dt$

$\displaystyle \frac{2}{3} \int t \cdot e^t \, dt$

now do parts ... let $\displaystyle u = t$ and $\displaystyle dv = e^t \, dt$ - Feb 25th 2009, 03:36 PMswensonm
Why did you solve for ds?

- Feb 25th 2009, 03:44 PMskeeter
because one cannot integrate a function of t w/respect to s.

- Feb 25th 2009, 05:55 PMswensonmThank You
Thanks skeeter. (Rofl)