(x-y)^3=

请问怎么拆

(x-y)^3
=(x-y)(x-y)²
=(x-y)(x²-2xy+y²)
=x(x²-2xy+y²)-y(x²-2xy+y²)
=x³-2x²y+xy²-x²y+2xy²-y³
=x³-3x²y+3xy²-y³

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第1个回答  2012-03-31
(x-y)³=x³-3x²y+3xy²-y³
第2个回答  2012-03-31
x³+xy²-2x²y-x²y-y³﹢2xy²
第3个回答  2012-03-31
(x-y)^3=x^3-3x^2y+3xy^2-y^3