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Date November 2018 Marks available 2 Reference code 18N.2.AHL.TZ0.H_6
Level Additional Higher Level Paper Paper 2 Time zone Time zone 0
Command term Find Question number H_6 Adapted from N/A

Question

Let P ( x ) = 2 x 4 15 x 3 + a x 2 + b x + c , where  a b c R

Given that  ( x 5 ) is a factor of P ( x ) , find a relationship between a , b and c .

[2]
a.

Given that ( x 5 ) 2 is a factor of P ( x ) , write down the value of P ( 5 ) .

[1]
b.

Given that ( x 5 ) 2 is a factor of P ( x ) , and that  a = 2 , find the values of  b and  c .

[3]
c.

Markscheme

* This question is from an exam for a previous syllabus, and may contain minor differences in marking or structure.

attempt to substitute  x = 5 and set equal to zero, or use of long / synthetic division      (M1)

2 × 5 4 15 × 5 3 + a × 5 2 + 5 b + c = 0       A1

( 25 a + 5 b + c = 625 )

 

[2 marks]

a.

0     A1

 

[1 mark]

b.

EITHER

attempt to solve  P ( 5 ) = 0      (M1)

8 × 5 3 45 × 5 2 + 4 × 5 + b = 0

 

OR

( x 2 10 x + 25 ) ( 2 x 2 + α x + β ) = 2 x 4 15 x 3 + 2 x 2 + b x + c       (M1)

comparing coefficients gives  α = 5, β  = 2

 

THEN

b = 105      A1

c = 625 25 × 2 525

c = 50      A1

 

[3 marks]

c.

Examiners report

[N/A]
a.
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b.
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c.

Syllabus sections

Topic 2—Functions » AHL 2.12—Factor and remainder theorems, sum and product of roots
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Topic 2—Functions

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