CAIE P3 2003 June — Question 3 4 marks

Exam BoardCAIE
ModuleP3 (Pure Mathematics 3)
Year2003
SessionJune
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicModulus function
TypeSolve |linear| compared to linear: algebraic only
DifficultyStandard +0.3 This is a straightforward modulus inequality requiring students to consider two cases (x ≥ 2 and x < 2) and solve linear inequalities in each case, then combine the solutions. It's slightly above average difficulty as it requires systematic case analysis and careful attention to the domain restrictions, but the algebraic manipulation is routine and the concept is a standard P3 topic.
Spec1.02l Modulus function: notation, relations, equations and inequalities

3 Solve the inequality \(| x - 2 | < 3 - 2 x\).

AnswerMarks Guidance
EITHER State or imply non-modular inequality \((x-2)^2 < (3-2x)^2\), or corresponding equationB1 Expand and make a reasonable solution attempt at a 2- or 3-term quadratic, or equivalent
OR State the relevant linear equation for a critical value, i.e. \(2 - x = 3 - 2x\), or equivalentB1 Obtain critical value \(x = 1\)
OR Obtain the critical value \(x = 1\) from a graphical method, or by inspection, or by solving a linear inequalityB2 State answer \(x < 1\)
**EITHER** State or imply non-modular inequality $(x-2)^2 < (3-2x)^2$, or corresponding equation | B1 | Expand and make a reasonable solution attempt at a 2- or 3-term quadratic, or equivalent | M1 | Obtain critical value $x = 1$ | A1 | State answer $x < 1$ only | A1 |

**OR** State the relevant linear equation for a critical value, i.e. $2 - x = 3 - 2x$, or equivalent | B1 | Obtain critical value $x = 1$ | B1 | State answer $x < 1$ | B1 | State or imply by omission that no other answer exists | B1 |

**OR** Obtain the critical value $x = 1$ from a graphical method, or by inspection, or by solving a linear inequality | B2 | State answer $x < 1$ | B1 | State or imply by omission that no other answer exists | B1 | **[4]**
3 Solve the inequality $| x - 2 | < 3 - 2 x$.

\hfill \mbox{\textit{CAIE P3 2003 Q3 [4]}}