$1) \begin{cases}(1-y)\sqrt{x-y} +x=2+(x-y-1)\sqrt{y}\\ 2y^2-3x+6y=1=2\sqrt{x-2y} -\sqrt{4x-5y-3}\end{cases}$$2)\begin{cases}\sqrt{x+1}+\sqrt[4]{x-1}-\sqrt{y^2+1} =y\\ x^2+2x(y-1)+y^2-6y+1=0 \end{cases}$$3\begin{cases}2x^2+y^2-3xy+3x-2y+1=0 \\ 4x^2-y^2+x+4=\sqrt{2x+y}\sqrt{x+4y} \end{cases}$