Mathematics 9709 · AS & A Level · Differentiation

Differentiation — practice question

The curve is described by $y = 4 + 5x + 6x^2 - 3x^3$.
(a)[4]

Find the set of x-values for which $y$ falls as $x$ increases.

(b)[4]

The line $y = 9x + k$ is tangent to the curve. Find the value of the constant $k$.

Worked solution & mark scheme

This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “After differentiation, the result is $5+12x-9x^2$” …

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