# calculus

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6. Determine a, b, c, and d so that the graph of y=ax^3+bx^2+cx+d has a point of inflection at the origin and a relative maximum at the point (2, 4). Sketch the graph.

• calculus -

y = ax^3 + bx^2 + cx + d
y' = 3ax^2 + 2bx + c
y'' = 6ax + 2b

y''(0) = 0
so b = 0

y'(2) = 0
so c = -12a

y(0) = 0
so d = 0

y = ax^3 - 12ax
y(2) = 4
so a = -1/4

y = -1/4 x^3 + 3x
y' = -3/4 x^2 + 3
y'' = -3/2 x

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