Mathematics 9709 · AS & A Level · Trigonometry

Trigonometry — practice question

The polynomial $p(x)$ is given by $p(x) = ax^3 + 3x^2 + bx + 12$, with $a$ and $b$ as constants. It is stated that $(x + 3)$ is a factor of $p(x)$, and that the remainder when $p(x)$ is divided by $(x + 2)$ is $18$.
(i)[5]

Find the values for $a$ and $b$.

(ii(a))[4]

Show that $p(x)=0$ has precisely one real root.

(ii(b))[3]

Solve $p(\sec y) = 0$ when $-180^{\circ} < y < 180^{\circ}$.

Worked solution & mark scheme

This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: Set $x=-3$, make the expression equal to zero and arrive at $27a+3b=39$ or equivalent

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