$7$ pt $]$ Compute the following integrals

a$.{}_T{e}^{(x-2y{)}^2}dA,$ where $T$ is the triangle bound by $x-2y=1,3x+y=0,$ and $x+5y=0$

b$.{}_D\frac{x-y}{x+y}dA,$ where $D$ is the square with vertices $(0,2),(1,1),(2,2),$ and $(1,3)$