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 ′′.

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