35: Derivative is
Critical points: f = 0 we cannot solve directly as equation.
However: We see that for x > 0 we get
f ′(x) > 0 and for
x < 0
we get f ′(x) < 0, so the value
f ′(0) = 0 is the only critical point.
There is no local maximum;
local minimum f (0) = 0.
Now determine concavity using f ′′.
Next hint
Answer