叫room不是叫床
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1/2=a^4/b .....(1)
1=a^5/b .....(2)
(2)/(1): 2=a, b=2^5=32
f(x)=2^x/2^5=2^(x-5)
y=log2[1-f(x)]=log2[1-2^(x-5)]
y'=[1-2^(x-5)]'/([1-2^(x-5)]ln2)
=-2^(x-5)ln2/([1-2^(x-5)]ln2)
=-2^(x-5)/[1-2^(x-5)]
由定义知,1-2^(x-5)>0, 2^(x-5)>0
所以 y'<0
所以 y 单调递减
1年前
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