[tex]\text{Mai intai hai sa explicitam modulul.} \\
f(x)= \left \{ {{\ln(x+1),x\geq -1} \atop ln(-1-x),x\ \textless \ -1}} \right.\\
\text{Prin urmare:}\\
f'(x)= \left \{ {{\dfrac{1}{x+1},x\geq -1} \atop {\dfrac{-1}{-x-1},x\ \textless \ -1}} \right. = \dfrac{1}{x+1}\ \forall x\ \in \mathbb{R}[/tex]