Giải hệ
1) $\left\{\begin{matrix} z(xy+1)=3+xy \\x(yz+1)=1+2xz \\y(xz+1)=2+3xy \end{matrix}\right.$
2) $\left\{\begin{matrix} xy(3x+y)=4\\7x^{3}+11=3(x+y)(x+y+1) \\ \end{matrix}\right.$
3) $\left\{\begin{matrix} x^{2}+y^{2}+3xy+1=(x+y)(2+xy)\\x^{3}+y^{3}=1 \end{matrix}\right.$