Giải các hệ phương trình sau:
1,$\left\{\begin{matrix} (x^2+1)y^4+1 &=2xy^2(y^3-1) \\ xy^2(3xy^4-2) & =xy^4(x+2y)+1 \end{matrix}\right.$
2,$\left\{\begin{matrix} xy & =5x+6\\-4y^2-10y-10 = & x^2-5xy \end{matrix}\right.$
3,$\left\{\begin{matrix} xy-2y-3=\sqrt{y-x-1}+ &\sqrt{y-3x+5} \\ (1-y)\sqrt{2x-y}+2(x-1) & =(2x-y-1)\sqrt{y} \end{matrix}\right.$
4,$\left\{\begin{matrix} \frac{x-y}{1-xy} & =\frac{5-y}{5y-1}\\\frac{x+y}{1+xy} = & \frac{x+5}{5x+1} \end{matrix}\right.$