22: Derivative is
Critical points: f = 0 for x = −1 and x = 1; f ′ is suspect at x = 0.
Local maximum f (0) = 0; local minimum f (−1) = −2 and f (1) = −2.
Remark: One-sided derivatives at the connecting point are
They are not equal, so there is really no derivative at x = 0.
Now determine concavity using f ′′.
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