(a+b)2=a2+2ab+b2 (a+b)3=?

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乘方的格式应该规范化：

a^3+3*a^2*b+3*a*b^2+b^3

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(a+b)2=a2+2ab+b2
(a+b)3=(a+b)( a2+2ab+b2)
=a3++2a2b+ab2+a2b+2ab2+b3
=a3+3a2b+3ab2+b3

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a3+b3+3a2b+3ab2

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