CAIE P2 2024 November — Question 4 8 marks

Exam BoardCAIE
ModuleP2 (Pure Mathematics 2)
Year2024
SessionNovember
Marks8
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicFactor & Remainder Theorem
TypeVerify, factorise, solve with substitution
DifficultyStandard +0.3 This is a straightforward multi-part question requiring standard techniques: using the factor theorem to find a constant (substitution and solving linear equation), factorising a cubic (by inspection or division), then solving a trigonometric equation by substitution. All steps are routine A-level procedures with no novel insight required, making it slightly easier than average.
Spec1.02j Manipulate polynomials: expanding, factorising, division, factor theorem1.05h Reciprocal trig functions: sec, cosec, cot definitions and graphs1.05o Trigonometric equations: solve in given intervals

4 The polynomial \(\mathrm { p } ( x )\) is defined by $$\mathrm { p } ( x ) = a x ^ { 3 } - a x ^ { 2 } - 15 x + 18$$ where \(a\) is a constant. It is given that ( \(x + 2\) ) is a factor of \(\mathrm { p } ( x )\).
  1. Find the value of \(a\).
  2. Hence factorise \(\mathrm { p } ( x )\) completely.
  3. Solve the equation \(\mathrm { p } \left( \operatorname { cosec } ^ { 2 } \theta \right) = 0\) for \(- 90 ^ { \circ } < \theta < 90 ^ { \circ }\).

Question 4(a):
AnswerMarks Guidance
AnswerMark Guidance
Substitute \(x = -2\), equate to zero and attempt solutionM1
Obtain \(a = 4\)A1
Question 4(b):
AnswerMarks Guidance
AnswerMark Guidance
Divide by \(x+2\) at least as far as \(k_1x^2 + k_2x\)M1
Obtain \(4x^2 - 12x + 9\)A1
Obtain \((x+2)(2x-3)^2\) or equivalent with integer coefficients onlyA1
Question 4(c):
AnswerMarks Guidance
AnswerMark Guidance
Equate \(\sin^2\theta\) to appropriate value from factorised form and attempt solutionM1 Using *their* \(\frac{2}{3}\)
Obtain \(54.7\)A1 Or greater accuracy
Obtain \(-54.7\)A1 Or greater accuracy. No others in \(-90° < \theta < 90°\)
## Question 4(a):

| Answer | Mark | Guidance |
|--------|------|----------|
| Substitute $x = -2$, equate to zero and attempt solution | M1 | |
| Obtain $a = 4$ | A1 | |

---

## Question 4(b):

| Answer | Mark | Guidance |
|--------|------|----------|
| Divide by $x+2$ at least as far as $k_1x^2 + k_2x$ | M1 | |
| Obtain $4x^2 - 12x + 9$ | A1 | |
| Obtain $(x+2)(2x-3)^2$ or equivalent with integer coefficients only | A1 | |

---

## Question 4(c):

| Answer | Mark | Guidance |
|--------|------|----------|
| Equate $\sin^2\theta$ to appropriate value from factorised form and attempt solution | M1 | Using *their* $\frac{2}{3}$ |
| Obtain $54.7$ | A1 | Or greater accuracy |
| Obtain $-54.7$ | A1 | Or greater accuracy. No others in $-90° < \theta < 90°$ |

---
4 The polynomial $\mathrm { p } ( x )$ is defined by

$$\mathrm { p } ( x ) = a x ^ { 3 } - a x ^ { 2 } - 15 x + 18$$

where $a$ is a constant. It is given that ( $x + 2$ ) is a factor of $\mathrm { p } ( x )$.
\begin{enumerate}[label=(\alph*)]
\item Find the value of $a$.
\item Hence factorise $\mathrm { p } ( x )$ completely.\\

\begin{center}

\end{center}
\item Solve the equation $\mathrm { p } \left( \operatorname { cosec } ^ { 2 } \theta \right) = 0$ for $- 90 ^ { \circ } < \theta < 90 ^ { \circ }$.
\end{enumerate}

\hfill \mbox{\textit{CAIE P2 2024 Q4 [8]}}