joint density function of X and Y:

$\displaystyle f(x,y)=\left\{

\begin{array}{lr}

k(x+y)&0\le x+y\le 1; x,y\ge 0\\

0&otherwise

\end{array}

\right.$

If I was looking for k, would $\displaystyle \int_0^{1-y} \int_0^{1-x} k(x+y) dy dx=1$ be the right way to start?