CAIE P3 2020 June — Question 1 4 marks

Exam BoardCAIE
ModuleP3 (Pure Mathematics 3)
Year2020
SessionJune
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicModulus function
TypeSolve k|linear| compared to |linear|
DifficultyStandard +0.8 This requires solving an inequality involving two modulus expressions, necessitating systematic case analysis across multiple critical points (x = 1/2 and x = -2), then solving quadratic inequalities in each region and combining solutions. More demanding than routine single-modulus problems but follows a standard technique for P3 level.
Spec1.02l Modulus function: notation, relations, equations and inequalities

1 Solve the inequality \(| 2 x - 1 | > 3 | x + 2 |\).

Question 1:
AnswerMarks Guidance
AnswerMark Guidance
State or imply non-modular inequality \((2x-1)^2 > 3^2(x+2)^2\), or corresponding quadratic equation, or pair of linear equationsB1
Make reasonable attempt at solving a 3-term quadratic, or solve two linear equations for \(x\)M1
Obtain critical values \(x = -7\) and \(x = -1\)A1
State final answer \(-7 < x < -1\)A1
Alternative method for Question 1:
AnswerMarks Guidance
AnswerMark Guidance
Obtain critical value \(x = -1\) from a graphical method, or by solving a linear equation or linear inequalityB1
Obtain critical value \(x = -7\) similarlyB2
State final answer \(-7 < x < -1\)B1 Do not condone \(\leqslant\) for \(<\) in the final answer
Total: 4 marks
## Question 1:

| Answer | Mark | Guidance |
|--------|------|----------|
| State or imply non-modular inequality $(2x-1)^2 > 3^2(x+2)^2$, or corresponding quadratic equation, or pair of linear equations | B1 | |
| Make reasonable attempt at solving a 3-term quadratic, or solve two linear equations for $x$ | M1 | |
| Obtain critical values $x = -7$ and $x = -1$ | A1 | |
| State final answer $-7 < x < -1$ | A1 | |

**Alternative method for Question 1:**

| Answer | Mark | Guidance |
|--------|------|----------|
| Obtain critical value $x = -1$ from a graphical method, or by solving a linear equation or linear inequality | B1 | |
| Obtain critical value $x = -7$ similarly | B2 | |
| State final answer $-7 < x < -1$ | B1 | Do not condone $\leqslant$ for $<$ in the final answer |

**Total: 4 marks**
1 Solve the inequality $| 2 x - 1 | > 3 | x + 2 |$.\\

\hfill \mbox{\textit{CAIE P3 2020 Q1 [4]}}