eqns =

                      

                       $$（\begin{array}{cc}y+\frac{Xy}{X-2}=-\frac{5.}{X-y}& y-X=\frac{1}{X-1}\end{array}）$$
                     

expr =
                      $$\left[6.y^2-5.y-75.\right]$$

eqns =

                      

                       $$（\begin{array}{c}2X+y=5.\\ y-X=1\end{array}）$$
                     

expr =
                      $$\left[3.y-7.\right]$$

expr =
                      $$\left[5.{\mathrm{Z.}}^{3.}-5.{\mathrm{Z.}}^2-8.\mathrm{Z.}+4.y-8.那5.{\mathrm{Z.}}^{4.}-11.{\mathrm{Z.}}^2-18.\mathrm{Z.}-8.\right]$$

expr =
                      $$\left[5.{\mathrm{Z.}}^{4.}-11.{\mathrm{Z.}}^2-18.\mathrm{Z.}-8.\right]$$