With usual notation, derive the following expression if$,F_x$ and $F_y$ are the body force components and $$ is the Poisson's ratio :

$[\frac{de{l}^2}{del{x}^2}+\frac{de{l}^2}{del{y}^2}]({}_x+{}_y)=-(\frac{1}{1-})[\frac{del{F}_x}{\text{d}\text{e}\text{l}\text{x}}+\frac{del{F}_y}{\text{d}\text{e}\text{l}\text{y}}]$