Date | November 2010 | Marks available | 4 | Reference code | 10N.1.hl.TZ0.1 |
Level | HL only | Paper | 1 | Time zone | TZ0 |
Command term | Find | Question number | 1 | Adapted from | N/A |
Question
Find the set of values of x for which |x−1|>|2x−1||x−1|>|2x−1|.
Markscheme
EITHER
|x−1|>|2x−1|⇒(x−1)2>(2x−1)2|x−1|>|2x−1|⇒(x−1)2>(2x−1)2 M1
x2−2x+1>4x2−4x+1x2−2x+1>4x2−4x+1
3x2−2x<03x2−2x<0 A1
0<x<230<x<23 A1A1 N2
Note: Award A1A0 for incorrect inequality signs.
OR
|x−1|>|2x−1||x−1|>|2x−1|
x−1=2x−1x−1=2x−1 x−1=1−2xx−1=1−2x M1A1
−x=0−x=0 3x=23x=2
x=0x=0 x=23x=23
Note: Award M1 for any attempt to find a critical value. If graphical methods are used, award M1 for correct graphs, A1 for correct values of x.
0<x<230<x<23 A1A1 N2
Note: Award A1A0 for incorrect inequality signs.
[4 marks]
Examiners report
This question turned out to be more difficult than expected. Candidates who squared both sides or drew a graph generally gave better solutions than those who relied on performing algebraic operations on terms involving modulus signs.