## Finding definite Integral Help

Limits, differentiation, related rates, integration, trig integrals, etc.
jdom543
Posts: 12
Joined: Tue Dec 01, 2009 3:05 am
Contact:

### Finding definite Integral Help

I need to find the definite integral of f(x)=xe^(4x) on the closed interval [-2,2]

I just recently learned how to find definite integrals but most of the ones I've learned weren't like this and are easier at least at first glance (Unless I'm missing something). I know how to use substitution and what not, but I don't see anything here to substitute to make the problem simpler. Thanks

Martingale
Posts: 350
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA
Contact:

### Re: Finding definite Integral Help

jdom543 wrote:I need to find the definite integral of f(x)=xe^(4x) on the closed interval [-2,2]

I just recently learned how to find definite integrals but most of the ones I've learned weren't like this and are easier at least at first glance (Unless I'm missing something). I know how to use substitution and what not, but I don't see anything here to substitute to make the problem simpler. Thanks

$\int\limits_{-2}^{2}xe^{4x}dx$

use integration by parts

jdom543
Posts: 12
Joined: Tue Dec 01, 2009 3:05 am
Contact:

### Re: Finding definite Integral Help

Martingale wrote:
jdom543 wrote:I need to find the definite integral of f(x)=xe^(4x) on the closed interval [-2,2]

I just recently learned how to find definite integrals but most of the ones I've learned weren't like this and are easier at least at first glance (Unless I'm missing something). I know how to use substitution and what not, but I don't see anything here to substitute to make the problem simpler. Thanks

$\int\limits_{-2}^{2}xe^{4x}dx$

use integration by parts

I haven't learned that yet. At least I don't think I guess I'll google/youtube it for a video on it. Thanks

Martingale
Posts: 350
Joined: Mon Mar 30, 2009 1:30 pm
Location: USA
Contact:

### Re: Finding definite Integral Help

jdom543 wrote:I haven't learned that yet. At least I don't think I guess I'll google/youtube it for a video on it. Thanks

stapel_eliz
Posts: 1738
Joined: Mon Dec 08, 2008 4:22 pm
Contact:
jdom543 wrote:I know how to use substitution and what not....
Martingale wrote:use integration by parts
jdom543 wrote:I haven't learned that yet.

What methods have you learned?

Thank you!

jdom543
Posts: 12
Joined: Tue Dec 01, 2009 3:05 am
Contact:

### Re:

stapel_eliz wrote:
jdom543 wrote:I know how to use substitution and what not....
Martingale wrote:use integration by parts
jdom543 wrote:I haven't learned that yet.

What methods have you learned?

Thank you!

The method that I learn usually only involved substitution of one term and then when you decide by the reciprocal derivative of that term it cancels out other terms in the integrand making it much easier to simplify. I've also know about substitution using Trig identities. And now I know Integration by parts since I looked up a video regarding it.