Rút gọn các biểu thức sau: (-3x^ny^n + 1/2x^ny^2n - 3)(-2x^2ny^n) + x^2ny^n(x^ny^2n +1)

Ta có: −3xnyn+12xny2n−3−2x2nyn+x2nynxny2n+1

           =−3xnyn.−2x2nyn+12xny2n.−2x2nyn−3−2x2nyn+x2nynxny2n+1

                   =6x3ny2n−x3ny3n+6x2nyn+x3ny3n+x3ny3n+x2nyn

                   =6x3ny2n+7x2nyn=x2nyn6xnyn+7