Math Help - Double Integrals Problem

1. Double Integrals Problem

I must solve the double integral -
∫ ∫ (x^2 + y^2) e^(-x^4 - 2(x^2)(y^2) - y^4) dy dx
Both integrals between infinity and - infinity!

2. Sorry, error

I have attempted to use x = rcos(theta) and y=rsin(theta) but cant seem to get an answer.

4. Hi. How about using polar coordinates? You know $x^2+y^2=r^2$ right? Then turn the crank:

$\int_{-\infty}^{\infty}\int_{-\infty}^{\infty} (x^2+y^2)e^{-(x^2+y^2)^2} dydx=\int_0^{2\pi}\int_0^{\infty}r^2 e^{-r^4}rdrdt$