已知(a+b)²=8,(a-b)²=2,求a³b³.
1个回答
2014-02-08
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(a+b)²=8=a²+2ab+b² (1)
(a-b)²=2=a²-2ab+b² (2)
(1)-(2) 得:
4ab = 8-2 =6
即:ab = 3/2
所以,a³b³ = (ab)³ = (3/2)³ = 27/8
(a-b)²=2=a²-2ab+b² (2)
(1)-(2) 得:
4ab = 8-2 =6
即:ab = 3/2
所以,a³b³ = (ab)³ = (3/2)³ = 27/8
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