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Local maximum of f at x = c (if f'(c) = 0):
Af''(c) > 0
Bf''(c) < 0 (concave down)
Cf''(c) = 0
Df'''(c) = 0
Answer & Solution
Correct answer: B. f''(c) < 0 (concave down)
Second derivative test: if f'(c) = 0 and f''(c) < 0, then c is a local max. If f''(c) > 0, c is local min. If f''(c) = 0, test inconclusive.
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