• May 8th 2008, 03:31 PM
BigBlack
e^-2.5xdx .... i got -5/2e^2,5x+c

Xcosx(3x^2)dx.... i got 1/12sin(3x^2) + c

(5x/x^2+1)dx

X(x^2-8)^1/2 dx

(1-e^-x/e^-x)dx

(3x-2)^5/2 dx
• May 8th 2008, 04:24 PM
o_O
Quote:

Originally Posted by BigBlack
e^-2.5xdx .... i got -5/2e^2,5x+c

(Yes)

Quote:

Originally Posted by BigBlack
Xcosx(3x^2)dx.... i got 1/12sin(3x^2) + c

I'm guessing you mean: $\int x\cos \left(3x^{2}\right) dx$

Check over your work again. The constant in front of your antiderivative is off. Show your work and we'll see if we can sort it out for you.

Quote:

Originally Posted by BigBlack
(5x/x^2+1)dx

$u = x^{2} + 1$

Quote:

Originally Posted by BigBlack
X(x^2-8)^1/2 dx

$u = x^{2} - 8$

Quote:

Originally Posted by BigBlack
(1-e^-x/e^-x)dx

Split the fraction: $\frac{1-e^{-x}}{e^{-x}} = \frac{1}{e^{-x}} - \frac{e^{-x}}{e^{-x}}$

And simplify.

Quote:

Originally Posted by BigBlack
(3x-2)^5/2 dx

$u = 3x - 2$