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ab>0,比较3√a-3√b与3√a-b的大小
人气:402 ℃ 时间:2020-05-16 15:39:36
解答
[a^(1/3)-b^(1/3)]^3=a-b+3(ab)^(1/3)(a^(1/3-b^(1/3))[(a-b)^(1/3)]^3=(a-b)[a^(1/3)-b^(1/3)]^3-[(a-b)^(1/3)]^3=3(ab)^(1/3)(a^(1/3-b^(1/3)) (1)因ab>0 所以当a>b>0,或0(a-b)^(1/3)当b>a>0,或0
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