FunctionProperty 希望杯 Intermediate
2012


Problem - 3674
Find the range of function $f(x)=3^{-|\log_2x|}-4|x-1|$.

It is easy to determine that $-4|x-1|$ will reach its maximum value of $0$ when $x=1$. Meanwhile, exponential function is monotonically increasing when its base is greater than $1$. Therefore, $3^{-|\log_2x|}$ will reach its maximum when $-|\log_2x|$ is the largest, or $x=1$. Hence, the $\max f(x) = f(1) = 1$. Obviously, the minimal value of $f(x)$ is $-\infty$ and this function is continuous on its entire domain which means its range is $\boxed{(-\infty, 1]}$.

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