Giải hpt:1.$\left\{ \begin{array}{l} x^2+y+x^3y+xy^2+xy=\frac{-5}{4}\\ x^4+y^2+xy.(1+2x)=\frac{-5}{4} \end{array} \right.$
2.$\left\{ \begin{array}{l} xy+x+y=x^2-2y^2\\ x\sqrt{2y}-y\sqrt{x-1}=2x-2y \end{array} \right.$
3.$\left\{ \begin{array}{l} xy+x+1=7y\\ x^2y^2+xy+1=13y^2 \end{array} \right.$
4.$\left\{ \begin{array}{l} x(x+y+1)-3=0\\ (x+y)^2-\frac{5}{x^2}+1=0 \end{array} \right.$