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a^3b+3a^2b^2+ab^3
=ab(a^2+3ab+b^2)
=ab[(a^2+2ab+b^2)+ab]
=ab[(a+b)^2+ab]
=3/8*[(1/2)^2+3/8]
=3/8*[1/4+3/8]
=3/8*5/8
=15/64
1年前
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http://zhidao.baidu.com/question/251403697.html http://zhidao.baidu.com/question/251403241.html?fr=middle_ask 去这两个网址看看,谢谢