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Date November 2021 Marks available 4 Reference code 21N.2.AHL.TZ0.10
Level Additional Higher Level Paper Paper 2 Time zone Time zone 0
Command term Find Question number 10 Adapted from N/A

Question

Consider the function fx=x2-x-122x-15, x, x152.

Find the coordinates where the graph of f crosses the

x-axis.

[2]
a.i.

y-axis.

[1]
a.ii.

Write down the equation of the vertical asymptote of the graph of f.

[1]
b.

The oblique asymptote of the graph of f can be written as y=ax+b where a, b.

Find the value of a and the value of b.

[4]
c.

Sketch the graph of f for -30x30, clearly indicating the points of intersection with each axis and any asymptotes.

[3]
d.

Express 1fx in partial fractions.

[3]
e.i.

Hence find the exact value of 031fxdx, expressing your answer as a single logarithm.

[4]
e.ii.

Markscheme

Note: In part (a), penalise once only, if correct values are given instead of correct coordinates.


attempts to solve x2-x-12=0              (M1)

-3,0 and 4,0             A1

 

[2 marks]

a.i.

Note: In part (a), penalise once only, if correct values are given instead of correct coordinates.

 

0,45            A1

 

[1 mark]

a.ii.

x=152            A1


Note: Award A0 for x152.
          Award A1 in part (b), if x=152 is seen on their graph in part (d).

[1 mark]

b.

METHOD 1

ax+b2x-15x2-x-12

attempts to expand ax+b2x-15              (M1)

2ax2-15ax+2bx-15bx2-x-12

a=12            A1

equates coefficients of x              (M1)

-1=-152+2b

b=134            A1

y=x2+134

 

METHOD 2

attempts division on x2-x-122x-15              M1

x2+134+              M1

a=12            A1

b=134            A1

y=x2+134

 

METHOD 3

a=12            A1

x2-x-122x-15x2+b+c2x-15              M1

x2-x-122x-15x2+2x-15b+c

equates coefficients of x :              (M1)

-1=-152+2b

b=134            A1

y=x2+134

 

METHOD 4

attempts division on x2-x-122x-15              M1

x2-x-122x-15=x2+13x2-122x-15

a=12            A1

13x2-122x-15=134+              M1

b=134            A1

y=x2+134

 

[4 marks]

c.

 

two branches with approximately correct shape (for -30x30)            A1

their vertical and oblique asymptotes in approximately correct positions with both branches showing correct asymptotic behaviour to these asymptotes            A1

their axes intercepts in approximately the correct positions            A1


Note: Points of intersection with the axes and the equations of asymptotes are not required to be labelled.

 

[3 marks]

d.

attempts to split into partial fractions:             (M1)

2x-15x+3x-4Ax+3+Bx-4

2x-15Ax-4+Bx+3

A=3             A1

B=-1             A1

3x+3-1x-4

 

[3 marks]

e.i.

033x+3-1x-4dx

attempts to integrate and obtains two terms involving ‘ln’             (M1)

=3lnx+3-lnx-403             A1

=3ln6-ln1-3ln3+ln4             A1

=3ln2+ln4  =ln8+ln4

=ln32  =5ln2             A1


Note: The final A1 is dependent on the previous two A marks.

 

[4 marks]

e.ii.

Examiners report

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

Syllabus sections

Topic 1—Number and algebra » SL 1.7—Laws of exponents and logs
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Topic 5 —Calculus » SL 5.11—Definite integrals, areas under curve onto x-axis and areas between curves
Topic 1—Number and algebra » AHL 1.11—Partial fractions
Topic 2—Functions » AHL 2.13—Rational functions
Topic 1—Number and algebra
Topic 2—Functions
Topic 5 —Calculus

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