1/ $\left\{\begin{matrix} 5x^2y-4xy^2+3y^3-2(x+y)=0 & \\ xy(x^2+y^2)+2=(x+y)^2 & \end{matrix}\right.$
2/ $\left\{\begin{matrix} \sqrt{x+y}+\sqrt{x+3}=\frac{y-3}{x} & \\ \sqrt{x+y}+\sqrt{x}=x+3 & \end{matrix}\right.$
3/ $\left\{\begin{matrix} xy+x-2=0 & \\ 2x^3-x^2y+x^2+y^2-2xy-y=0 & \end{matrix}\right.$