If $f$ and $g$ are two real valued positive functions. I need to prove the inequality $\max\limits_x|f(x)-g(x)|\geq |\min\limits_x f(x) - \min\limits_x g(x)| $. I am not able to get any counter example disproving the statement.
2026-04-09 00:01:20.1775692880
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Absolute value of difference of minimums of two functions is bounded above by their maximum absolute difference
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Without loss of generality suppose $\min_x f(x) \ge \min_x g(x)$. Let $x_0$ be such that $g(x_0) = \min_x g(x)$. Then $$|\min_x f(x) - \min_x g(x)| = \min_x f(x) - g(x_0) \le f(x_0) - g(x_0) \le \max_x |f(x) - g(x)|.$$
(I was a little un-rigorous in assuming that $g$ attains its infimum, but the argument can be modified appropriately.)
WLOG, assume that $f(x_1)=\min f(x)>\min g(x)=g(x_2)$, then $$\max |f(x)-g(x)|\geq |f(x_2)-g(x_2)|\geq f(x_2)-g(x_2)\geq f(x_1)-g(x_2)$$