已知xy^2=-6,求-xy(x^3y^7-3x^2y^5-y）的值
问题描述：
已知xy^2=-6,求-xy(x^3y^7-3x^2y^5-y）的值
答
xy^2=-6 (xy^2)^2=(-6)^2即x^2y^4=36 (xy^2)^3=(-6)^3即x^3y^6=-216 -xy(x^3y^7-3x^2y^5-y) =-xy[(x^3y^6)*y-3(x^2y^4)*y-y] =-xy[(xy^2)^3*y-3(xy^2)^2*y-y] =-xy(-216*y-3*36*y-y) =-xy*(-325y) =325xy^2 =325*(-6...