f(x)≥0<=>eˣ-1-x-x²/2≥0
f derivabila pe R(operatii cu functii elementare)
f'(x)=eˣ-x-1
f(0)=0;f'(0)=0=>0->punct de extrem=O(0;0)
[tex]\lim_{x \to \pm \infty}f(x)=\pm\infty[/tex]
f'(-1)<0
f'(1)>0
Din tabel=>f(x)≥f(0),∀x∈R<=>eˣ-1-x-x²/2≥0,∀x∈R=>f(x)≥0,∀x∈R