Answer
\[\int_{0}^{1}{\int_{0}^{y\left( 1-y \right)}f(x,y) {dx}dy}\]
Work Step by Step
\[\begin{align}
& \text{From the graph, the region }R\text{ is} \\
& R=\left\{ \left( x,y \right):0\le x\le y\left( 1-y \right),\text{ }0\le y\le 1\text{ } \right\} \\
& \text{Then,} \\
& \int_{0}^{1}{\int_{0}^{y\left( 1-y \right)}f(x,y) {dx}dy} \\
\end{align}\]
