CAIE P3 2013 June — Question 1 4 marks

Exam BoardCAIE
ModuleP3 (Pure Mathematics 3)
Year2013
SessionJune
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicModulus function
TypeSolve |linear| > |linear|
DifficultyStandard +0.3 This is a straightforward modulus inequality requiring consideration of critical points (x = 0 and x = -3/4) and testing regions, which is a standard technique taught in P3. While it requires systematic case analysis, it's a routine application of modulus inequality methods with no novel insight needed, making it slightly easier than average.
Spec1.02l Modulus function: notation, relations, equations and inequalities

1 Solve the inequality \(| 4 x + 3 | > | x |\).

AnswerMarks Guidance
State or imply non-modular inequality \((4x + 3)^2 > x^2\), or corresponding equation or pair of equations \(4x + 3 = \pm x\)M1
Obtain a critical value, e.g. \(-1\)A1
Obtain a second critical value, e.g. \(-\frac{3}{5}\)A1
State final answer \(x < -1, x > -\frac{3}{5}\)A1 [4 marks total]
OR:
AnswerMarks Guidance
Obtain critical value \(x = -1\), by solving a linear equation or inequality, or from a graphical method or by inspectionB1
Obtain the critical value \(-\frac{3}{5}\) similarlyB2
State final answer \(x < -1, x > -\frac{3}{5}\)B1 [4 marks total]
Guidance: Do not condone \(\leq\) or \(\geq\)
State or imply non-modular inequality $(4x + 3)^2 > x^2$, or corresponding equation or pair of equations $4x + 3 = \pm x$ | M1 |
Obtain a critical value, e.g. $-1$ | A1 |
Obtain a second critical value, e.g. $-\frac{3}{5}$ | A1 |
State final answer $x < -1, x > -\frac{3}{5}$ | A1 | [4 marks total]

**OR:**

Obtain critical value $x = -1$, by solving a linear equation or inequality, or from a graphical method or by inspection | B1 |
Obtain the critical value $-\frac{3}{5}$ similarly | B2 |
State final answer $x < -1, x > -\frac{3}{5}$ | B1 | [4 marks total]

**Guidance:** Do not condone $\leq$ or $\geq$

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1 Solve the inequality $| 4 x + 3 | > | x |$.

\hfill \mbox{\textit{CAIE P3 2013 Q1 [4]}}