# U-sub or integration by parts?

• Apr 24th 2010, 05:40 PM
RET80
U-sub or integration by parts?
I have this equation here...

(x/3)e^(x^2)

I'm thinking I have to take this in parts, am I right?
since isn't integration by parts the anti - product rule? and I see two products of x in this...

or am I totally wrong?

if it IS integration by parts....
which do I choose for u and dv

I think I have u = (1/3)x
du = 1/3dx
dv = x^2
v = (1/3)x^3

Will this work? I need to know how to recognize between u-sub and integration by parts and WHAT to take...
• Apr 24th 2010, 06:10 PM
harish21
Quote:

Originally Posted by RET80
I have this equation here...

(x/3)e^(x^2)

I'm thinking I have to take this in parts, am I right?
since isn't integration by parts the anti - product rule? and I see two products of x in this...

or am I totally wrong?

if it IS integration by parts....
which do I choose for u and dv

I think I have u = (1/3)x
du = 1/3dx
dv = x^2
v = (1/3)x^3

Will this work? I need to know how to recognize between u-sub and integration by parts and WHAT to take...

$\int \frac{x}{3} e^{x^2} dx = \frac{1}{3} \int x \times e^{x^2} dx$

use substitution, not integration by parts.
• Apr 25th 2010, 03:34 AM
HallsofIvy
Quote:

Originally Posted by RET80
I have this equation here...

(x/3)e^(x^2)

I'm thinking I have to take this in parts, am I right?
since isn't integration by parts the anti - product rule? and I see two products of x in this...

or am I totally wrong?

if it IS integration by parts....
which do I choose for u and dv

I think I have u = (1/3)x
du = 1/3dx
dv = x^2
v = (1/3)x^3

Will this work?

Well, why don't you try it and SEE if it works?