Math problem I need help with....

I need to integrate (x+y)e^(-x^2 - y^2) dxdy with the bounds x-y=0, x-2=y, x+y=0 and   3-x=y

I did the sbtitution u=x-y and v=x+y... It gives you x=(v-u)/2 and y=(v+u)/2

The Jacobian?(Im french dont know the english term) is 1/2.

The intergral now becomes 1/2 S(ve^((-u^2 - v^2)/2)dvdu) where u varies from 0 to 2 and v varies from 0 to 3.

then I go 1/2 S e^(-u^2) (e^(-v^2)|evaluated from 3 to 0

It gives 1/2(1-e^(-9/2))Se^(-u^2)du where u varies from 0 to 2

How do I integrate Se^(-u^2)du where u varies from 0 to 2?

when I try, I get sqrt(2Pi(1-e^(-4)))

so my answer is 1/2sqrt(2Pi(1-e^(-4)))(1-e^(-9/2))

but a computer program gives me 1/4 erf(sqrt(2)) sqrt(2Pi)(1-e^(-9/2))

Where do I go wrong??? How do I intergrate Se^(-u^2)du where u varies from 0 to 2?

Just do u own homework.

If you look at your solution and the computer solution you will notice that the difference is a factor of 2 and the mysterious erf thing. Look up erf in your math software manual and that may shed some light on what is happening.

Tha's a good one,lol,nice joke!

Lol, the teacher canceld the number 24hours before the homework was over because it was to hard, all the time I spent on it was for nothing, anyways, id still like to know.

I know the erf(oo) = 1

But in the definition that the computer gives me of erf(), theres the exact integral I cant do....but from 0 to sqrt 2.... anyhow...

I know that the integral of the thing from -oo to oo is sqrt of Pi....

o now thats its not a homework anymor, can someone give me the answer?