Moderate -0.3 This is a standard C3 modulus question requiring a routine sketch and solving two linear modulus inequalities using the V-shaped graph or algebraic cases. Part (a) is straightforward, parts (b) and (c) require splitting into cases or graphical interpretation but follow textbook methods with no novel insight required. Slightly easier than average due to the linear nature and standard technique application.
5. (a) Sketch the graph with equation
$$y = | 4 x - 3 |$$
stating the coordinates of any points where the graph cuts or meets the axes.
Find the complete set of values of \(x\) for which
(b)
$$| 4 x - 3 | > 2 - 2 x$$
(c)
$$| 4 x - 3 | > \frac { 3 } { 2 } - 2 x$$
Touches \(x\)-axis at \(\frac{3}{4}\) and cuts \(y\)-axis at \(3\)
B1
Question 5(b):
Answer
Marks
Guidance
Answer/Working
Mark
Guidance
Solves \(4x-3=2-2x\) or \(3-4x=2-2x\) to give either value of \(x\)
M1
Both \(x=\frac{5}{6}\) and \(x=\frac{1}{2}\), or \(x>\frac{5}{6}\) or \(x<\frac{1}{2}\)
A1
\(x<\frac{1}{2}\) or \(x>\frac{5}{6}\)
dM1 A1
Question 5(c):
Answer
Marks
Guidance
Answer/Working
Mark
Guidance
Draws graph or solves \(
4x-3
=1\frac{1}{2}-2x\) to give one solution \(x=\frac{3}{4}\)
All values of \(x\) except \(x=\frac{3}{4}\), i.e. \(x\neq\frac{3}{4}\), or \(x<\frac{3}{4}\), \(x>\frac{3}{4}\)
A1
Question 5 (Absolute Value/Modulus):
Part (a):
Answer
Marks
Guidance
Answer
Mark
Guidance
V-shaped graph
B1
Must be V-shape, not a curve. Accept V shape with dotted extension of \(y = 4x-3\) under x-axis
Meets x-axis at \(x = \frac{3}{4}\), crosses y-axis at \(y = 3\)
B1
\(A = \left(\frac{3}{4}, 0\right)\) and \(B = (0,3)\). Condone \(\left(0, \frac{3}{4}\right)\) and \((3,0)\) marked on correct axis
Part (b):
Answer
Marks
Guidance
Answer
Mark
Guidance
Attempts to solve \(
4x-3
\ldots 2-2x\), finding at least one solution
Both critical values \(x = \frac{5}{6}\) and \(x = \frac{1}{2}\)
A1
Accept \(x = 0.83\) and \(x = 0.5\). Or one inequality \(x > \frac{5}{6}\) or \(x < \frac{1}{2}\)
Selects outside region
dM1
Dependent on previous M. E.g. if \(x = 0.83\) and \(x = -2.5\) found, correct application gives \(x < -2.5, x > 0.83\)
\(x < \frac{1}{2}\) or \(x > \frac{5}{6}\)
A1
Accept \(x < 0.5, x > 0.83\)
Part (c):
Answer
Marks
Guidance
Answer
Mark
Guidance
Sketch both lines showing single intersection at \(x = \frac{3}{4}\), or solves \(
4x-3
= 1\frac{1}{2} - 2x\) using both \(4x-3 = 1\frac{1}{2}-2x\) and \(-4x+3 = 1\frac{1}{2}-2x\) giving one solution
Solution set is all values apart from \(x = \frac{3}{4}\)
A1
Accept: all values of \(x\) except \(x = \frac{3}{4}\), or \(x \in \mathbb{R},\ x \neq \frac{3}{4}\), or \(x < \frac{3}{4},\ x > \frac{3}{4}\)
# Question 5(a):
| Answer/Working | Mark | Guidance |
|---|---|---|
| V shaped graph | B1 | |
| Touches $x$-axis at $\frac{3}{4}$ and cuts $y$-axis at $3$ | B1 | |
# Question 5(b):
| Answer/Working | Mark | Guidance |
|---|---|---|
| Solves $4x-3=2-2x$ or $3-4x=2-2x$ to give either value of $x$ | M1 | |
| Both $x=\frac{5}{6}$ and $x=\frac{1}{2}$, or $x>\frac{5}{6}$ or $x<\frac{1}{2}$ | A1 | |
| $x<\frac{1}{2}$ or $x>\frac{5}{6}$ | dM1 A1 | |
# Question 5(c):
| Answer/Working | Mark | Guidance |
|---|---|---|
| Draws graph or solves $|4x-3|=1\frac{1}{2}-2x$ to give one solution $x=\frac{3}{4}$ | M1 | |
| All values of $x$ except $x=\frac{3}{4}$, i.e. $x\neq\frac{3}{4}$, or $x<\frac{3}{4}$, $x>\frac{3}{4}$ | A1 | |
# Question 5 (Absolute Value/Modulus):
## Part (a):
| Answer | Mark | Guidance |
|--------|------|----------|
| V-shaped graph | B1 | Must be V-shape, not a curve. Accept V shape with dotted extension of $y = 4x-3$ under x-axis |
| Meets x-axis at $x = \frac{3}{4}$, crosses y-axis at $y = 3$ | B1 | $A = \left(\frac{3}{4}, 0\right)$ and $B = (0,3)$. Condone $\left(0, \frac{3}{4}\right)$ and $(3,0)$ marked on correct axis |
## Part (b):
| Answer | Mark | Guidance |
|--------|------|----------|
| Attempts to solve $|4x-3| \ldots 2-2x$, finding at least one solution | M1 | Accept $\pm4x \pm 3 = 2-2x \Rightarrow x = ..$ or $\pm4x \pm 3 > 2-2x \Rightarrow x > ..$ or $x < ..$ |
| Both critical values $x = \frac{5}{6}$ and $x = \frac{1}{2}$ | A1 | Accept $x = 0.83$ and $x = 0.5$. Or one inequality $x > \frac{5}{6}$ or $x < \frac{1}{2}$ |
| Selects outside region | dM1 | Dependent on previous M. E.g. if $x = 0.83$ and $x = -2.5$ found, correct application gives $x < -2.5, x > 0.83$ |
| $x < \frac{1}{2}$ or $x > \frac{5}{6}$ | A1 | Accept $x < 0.5, x > 0.83$ |
## Part (c):
| Answer | Mark | Guidance |
|--------|------|----------|
| Sketch both lines showing single intersection at $x = \frac{3}{4}$, **or** solves $|4x-3| = 1\frac{1}{2} - 2x$ using both $4x-3 = 1\frac{1}{2}-2x$ and $-4x+3 = 1\frac{1}{2}-2x$ giving one solution | M1 | If two values obtained it is M0A0 |
| Solution set is all values apart from $x = \frac{3}{4}$ | A1 | Accept: all values of $x$ except $x = \frac{3}{4}$, or $x \in \mathbb{R},\ x \neq \frac{3}{4}$, or $x < \frac{3}{4},\ x > \frac{3}{4}$ |
---
5. (a) Sketch the graph with equation
$$y = | 4 x - 3 |$$
stating the coordinates of any points where the graph cuts or meets the axes.
Find the complete set of values of $x$ for which\\
(b)
$$| 4 x - 3 | > 2 - 2 x$$
(c)
$$| 4 x - 3 | > \frac { 3 } { 2 } - 2 x$$
\hfill \mbox{\textit{Edexcel C3 2014 Q5 [8]}}