(x-y)^3展开后的公式是什么?(x+y)^3呢 - 知识问答

(x-y)^3展开后的公式是什么?(x+y)^3呢?

3个回答

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

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