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已知a=㏒0.7(0.8) b=㏒1.1(0.9) c=1.1∧0.9 试比较a、b、c的大小
人气:350 ℃ 时间:2020-05-21 02:27:26
解答
a = ㏒0.7(0.8)= ln0.8/ln0.7 = 0.62562...
b = ㏒1.1(0.9)= ln0.9/ln1.1 = -1.1054...
lnc = 0.9ln1.1 = 0.085779182...
∴ c = 1.1^0.9 = e^0.085779182... = 1.0895684.
∴ c > a > b
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