Show $1-1/x <\ln(x)
for all $x>1$?
My attempt:
(1) $\ln (x)
Suppose $h: \mathbb{R}^+ \to \mathbb{R}, t\mapsto t-1-\ln(t)$, then $h'(t)=0$ if $t=1$. Furthermore $h'(t)>0$ for all $t\in \mathbb{R}^+$.
(2) $1-1/x<\ln(x)$
Suppose $f: \mathbb{R}^+\to \mathbb{R}, t\mapsto \ln(t)-1+\frac{1}{t}$, then $f'(t)=0$ for $t=1$ and $f'(t)>0$ for all $t\in \mathbb{R}^+$.
Therefore the inequality is true.
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