Thread: help evaluating a double integral

heres the integral

x is between 0 and 2
y is between 0 and 5x

I need to find the exact value of the double integral 5x^2e^(xy)

I'm not really sure how to do this so any help would be greatly appreciated. Thanks in advance.

Originally Posted by ryu991

heres the integral

x is between 0 and 2
y is between 0 and 5x

I need to find the exact value of the double integral 5x^2e^(xy)

I'm not really sure how to do this so any help would be greatly appreciated. Thanks in advance.

.

Where are you stuck in the calculation? If you showed us any attempt you made at the problem, it would give us a better idea of how to best help you.

Get the idea?

Thank you, what I didn't realize was to factor out the 5x^2, I was staring at the whole integral and I had no idea how to approach it I was thinming integration by parts or something but it just did not seem right.

Originally Posted by qmech

[tex]




Get the idea?

just a few questions about the end?

first where does the 1/2 come from?

second how would I integrate that expression e^(5x^2)d(5x^2)? The other half of it I know, i just have a lot of trouble integrating expressions with e.

thanks again for helping me with this.

is another way to write u-substitution where .

Originally Posted by lvleph

is another way to write u-substitution where .

so after the u substitution I would have to evaluate

(1/2)e^(5x^2) - (5/2)x^2 from 0 -2? making my answer be

[(1/2)e^20 -10] - [(1/2)e^0 - 0]

or whatever that evaluates to? or did I make a mistake along the way?

As long as you meant then yes.

Originally Posted by lvleph

As long as you meant then yes.

yeah thats what I meant(I saw what the syntax error was when I quoted you) thanks for all of your help.