(1/4)^x ≤1%
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(1/4)^x ≤1%
(1/4)^x ≤1%
(1/4)^x ≤1%
利用两边取对数的方法
(1/4)^x≤1%
两边取倒数
∴ 4^x≥100
两边取以4为底的对数
则 log4(4^x)≥log4(100)
即 x≥log4(100)
两边取对数 取以1/4为底的对数 左边就直接为x'右边进行变形'注意会有负号'且以1/4为底的对数为减函数
楼上所答即是
-x㏒4≤㏒(1%)
-x㏒4≤㏒(1/100)
-x㏒4≤-2
x㏒4≥2
x≥2/㏒4
x≥3.3219
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