Bonsoir,
f(x) = (x + 2) * exp^-x
f est de la forme u * v avec u = x + 2 et v = exp^-x
u' = 1 et v' = - exp^-x
(uv)' = u'v + uv'
f'(x) = exp^-x - exp^-x * (x+2)
f'(x) = exp^-x - x * exp^-x - 2exp^-x
f'(x) = -x * exp^-x - exp^-x
f'(x) = exp^-x (-x - 1)
