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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 |x1|>|2x1||x1|>|2x1|.

Markscheme

EITHER

|x1|>|2x1|(x1)2>(2x1)2|x1|>|2x1|(x1)2>(2x1)2     M1

x22x+1>4x24x+1x22x+1>4x24x+1

3x22x<03x22x<0     A1

0<x<230<x<23     A1A1     N2

Note: Award A1A0 for incorrect inequality signs.

 

OR

|x1|>|2x1||x1|>|2x1|

x1=2x1x1=2x1     x1=12xx1=12x     M1A1

x=0x=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.

Syllabus sections

Topic 2 - Core: Functions and equations » 2.7 » Solutions of g(x)f(x) .

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