Question

已知xy^2=-3,求-xy(x^2y^7-3x^2y^5-y)

Answer 1

=27y²-84

方法如下，请作参考：

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Answer 2

-xy(x^2y^7-3x^2y^5-y)
=-xy^2(x^2y^6-3x^2y^4-1)
=3(x^2y^4*y^2-3x^2y^4-1)
=3(9y^2-27-1)
=27y^2-84