[tex]\it f(x) = e^x-e^{-x}
\\\;\\
f'(x) =(e^x)'-(e^{-x})' = e^x-(-e^{-x}) =e^x+e^{-x} =e^x+\dfrac{1}{e^x} \ \textgreater \ 0
\\\;\\
f'(x) \ \textgreater \ 0,\ \forall\ x\in\mathbb{R} \Longrightarrow f(x) \ strict \ cresc\breve{\it a}toare\ pe \ \mathbb{R}
[/tex]
