- (E) Since the curve has a positive y-intercept, e > 0. Note that f ′(x) = 2cx + d and f ′′(x) = 2c.
Since the curve is concave down, f ′′(x) < 0, implying that c < 0. Since the curve is
decreasing at x = 0, f ′(0) must be negative, implying, since f ′(0) = d, that d < 0. Therefore c
< 0, d < 0, and e > 0.
dmanu
(dmanu)
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