已知xy^2=-6,求-xy(x^3y^7-3x^2y^5-y)的值
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已知xy^2=-6,求-xy(x^3y^7-3x^2y^5-y)的值
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)
=-1950
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