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Date May Example questions Marks available 6 Reference code EXM.1.AHL.TZ0.3
Level Additional Higher Level Paper Paper 1 (without calculator) Time zone Time zone 0
Command term Express Question number 3 Adapted from N/A

Question

Let  f ( x ) = 4 x 5 x 2 3 x + 2       x 1 , x 2 .

Express f ( x ) in partial fractions.

[6]
a.

Use part (a) to show that f ( x ) is always decreasing.

[3]
b.

Use part (a) to find the exact value of  1 0 f ( x ) d x , giving the answer in the form  ln q ,    q Q .

[4]
c.

Markscheme

f ( x ) = 4 x 5 ( x 1 ) ( x 2 ) A x 1 + B x 2    M1A1

4 x 5 A ( x 2 ) + B ( x 1 )      M1A1

x = 1 A = 1       x = 2 B = 3       A1A1

f ( x ) = 1 x 1 + 3 x 2

[6 marks]

a.

f ( x ) = ( x 1 ) 2 3 ( x 2 ) 2    M1A1

This is always negative so function is always decreasing.     R1AG

[3 marks]

b.

1 0 1 x 1 + 3 x 2   d x = [ ln | x 1 | + 3 ln | x 2 | ] 1 0    M1A1

= ( 3 ln 2 ) ( ln 2 + 3 ln 3 ) = 2 ln 2 3 ln 3 = ln 4 27     A1A1

[4 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Topic 1—Number and algebra » AHL 1.11—Partial fractions
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Topic 1—Number and algebra

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