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Date November 2017 Marks available 3 Reference code 17N.1.SL.TZ0.T_11
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number T_11 Adapted from N/A

Question

A quadratic function f is given by f ( x ) = a x 2 + b x + c . The points ( 0 ,   5 ) and ( 4 ,   5 ) lie on the graph of y = f ( x ) .

The y -coordinate of the minimum of the graph is 3.

Find the value of a and of b .

Markscheme

b 2 a = 2

a ( 2 ) 2 2 b + 5 = 3 or equivalent

a ( 4 ) 2 4 b + 5 = 5 or equivalent

2 a ( 2 ) + b = 0 or equivalent     (M1)

 

Note:     Award (M1) for two of the above equations.

 

a = 0.5     (A1)(ft)

b = 2     (A1)(ft)     (C3)

 

Note:     Award at most (M1)(A1)(ft)(A0) if the answers are reversed.

Follow through from parts (a) and (b).

 

[3 marks]

Examiners report

[N/A]

Syllabus sections

Topic 2—Functions » SL 2.5—Modelling functions
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