Use Jensen's inequality to show $\frac{2x}{2+x} < \log(1+x) < \frac{2x+x^2}{2+2x}$ for $x>0$.
I can show this without Jensen's inequality, but I'd like to see what that form of the proof looks like.
Without Jensen's, start with the inequality $\log(1+x) < x$ for $x>0$, integrate both sides to arrive at the upper bound. Also, $\log(1+x) > 1-\frac{1}{x+1}$ for $x>0$ (by substituting $x=1/u-1$ into the previous inequality). Integrate both sides to arrive at the lower bound.
Hermite-Hadamard inequality :
Now take $f(x)=\frac{1}{x}$ and $a=1$ and $b=x+1$ to get a lower and a upper bound . Without this refinement I think it's hopeless .