Question

Question See below

Answer 1

Let D be the region \[0 \le y \le x, 0 \le x \le 1\] Evaluate

\[\int\limits_{}^{}\int\limits_{}^{}(x+y) dxdy\]
by making changes of variables x=u+v
y = u-v
Check your answers by evaluating the integral directly by using an iterated integral

please explain each step you did thanks