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Date November 2018 Marks available 1 Reference code 18N.1.SL.TZ0.S_8
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Write down Question number S_8 Adapted from N/A

Question

Let  f ( x ) = x 2 4 x 5 . The following diagram shows part of the graph of f .

The function can be written in the form f ( x ) = ( x h ) 2 + k .

Find the equation of the axis of symmetry of the graph of f .

[2]
b.

Write down the value of h .

[1]
c.i.

Find the value of k .

[3]
c.ii.

The graph of a second function, g , is obtained by a reflection of the graph of f in the y -axis, followed by a translation of ( 3 6 ) .

 

Find the coordinates of the vertex of the graph of g .

[5]
d.

Markscheme

correct working      (A1)

eg    ( 4 ) 2 ( 1 ) ,   1 + 5 2

 

x = 2   (must be an equation with x = )      A1 N2

 

[2 marks]

b.

h = 2      A1  N1

 

[1 mark]

c.i.

METHOD 1

valid approach      (M1)

eg    f (2)

correct substitution      (A1)

eg   (2)2 − 4(2) − 5

k = −9     A1 N2

 

METHOD 2

valid attempt to complete the square      (M1)

eg    x 2 − 4 x + 4

correct working      (A1)

eg  ( x 2 − 4 x + 4) − 4 − 5,  ( x  − 2)2 − 9

k = −9     A1 N2

 

[3 marks]

c.ii.

 

METHOD 1 (working with vertex)

vertex of f is at (2, −9)      (A1)

correct horizontal reflection      (A1)

eg  x = −2,  (−2, −9)

valid approach for translation of their  x or y value      (M1)

eg    x  − 3,  y + 6,  ( 2 9 ) + ( 3 6 ) ,  one correct coordinate for vertex

vertex of g is (−5, −3) (accept x = −5, y = −3)      A1A1 N1N1

 

METHOD 2 (working with function)

correct approach for horizontal reflection      (A1)

eg    f (− x )

correct horizontal reflection      (A1)

eg   (− x )2 −4(− x ) − 5,    x + 4 x  − 5, (− x  − 2)2 − 9

valid approach for translation of their  x  or  y value      (M1)

eg   ( x + 3)2 + 4( x  + 3) − 5 + 6,  x 2 + 10 x + 22,  ( x + 5)2 − 3,  one correct coordinate for vertex

vertex of g is (−5, −3) (accept x = −5, y = −3)      A1A1 N1N1

 

[5 marks]

d.

Examiners report

[N/A]
b.
[N/A]
c.i.
[N/A]
c.ii.
[N/A]
d.

Syllabus sections

Topic 2—Functions » SL 2.5—Modelling functions
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Topic 2—Functions » AHL 2.8—Transformations of graphs, composite transformations
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