化简。3(xy平方-x平方y)+2(x平方y-xy)平方 (3a平方-ab+7)-(-4a平方+2ab+7)过程,急!

如题所述

解1 3(xy^2-x^2y)+2(x^2y-xy^2)
=3xy^2-3x^2y+2x^2y-2xy^2
=xy^2-x^2y
=xy(y-x)
解2 (2a^2-ab+7)-(-4a^2+2ab+7)
=2a^2-ab+7+4a^2-2ab-7
=6a^2-3ab
=3a(2a-b)
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