
Re: [中學] 曲線問題一問

y_1 = [2^(x) + 2^(-x)] / 2 >= 1
y_2 = k / [2^(x) + 2^(-x)] <= k / 2
x = |a|如為y_1 = y_2的解
則x = -|a|也必為一解
=> 2|a| = 2
=> |a| = 1
[2 + 1/2] / 2 = 5/4
= k / [2 + 1/2]
=> k = (5/4)[5/2]
= 25/8
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