Use the transformation:

x = (u+v)/2

y = (v−u)/2

double integral bounded by R of: (x − y)(x + y)dxdy

where R is the region bounded by the lines y = x + 2, y = x, y = −x + 2 and

y = −x + 4.

Again...its the bounds of the integral that are killing me. Thanks ahead of time my book is just terrible.