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Date May 2022 Marks available 4 Reference code 22M.1.AHL.TZ1.14
Level Additional Higher Level Paper Paper 1 Time zone Time zone 1
Command term Find Question number 14 Adapted from N/A

Question

The region bounded by y=1x+2+1, x=0, x=2 and the x-axis is rotated through 2π about the x-axis to form a solid.

Expand 1u+12.

[1]
a.i.

Find 1x+2+12dx.

[3]
a.ii.

Find the volume of the solid formed. Give your answer in the form π4a+blnc, where a, b, c.

[4]
b.

Markscheme

1u2+2u+1             A1

 

[1 mark]

a.i.

1x+2+12dx

=1x+22+2x+2+1dx   OR   1u2+2u+1du             (M1)

=-1x+2+2lnx+2+x+c             A1A1


Note:
Award A1 for first expression, A1 for second two expressions.
Award A1A0 for a final answer of =-1u+2lnu+u+c.


[3 marks]

a.ii.

volume =π-1x+2+2lnx+2+x02             M1

=π-14+2ln4+2+12-2ln2             A1

=π94+2ln4-2ln2

use of log laws seen, for example             M1

π94+4ln2-2ln2   OR   π94+2ln42

=π49+8ln2   OR   a=9, b=8 and c=2             A1


Note:
Other correct integer solutions are possible and should be accepted for example a=9, b=c=4.

 

[4 marks]

b.

Examiners report

Some candidates could answer part (a) (i). The link between parts (i) and (ii) was, however, lost to the majority. Those who did see the link were often able to give a reasonable answer to (ii). But some candidates lacked the skills to integrate without the use of technology, so an indefinite integral presented many problems. Even those who successfully navigated part (a) went on to fail to see the link to part (b). Either the integration was attempted as something totally new and unconnected or it was simply found with the GDC which did not lead to a final answer in the required form.

a.i.
[N/A]
a.ii.
[N/A]
b.

Syllabus sections

Topic 5—Calculus » AHL 5.12—Areas under a curve onto x or y axis. Volumes of revolution about x and y
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Topic 5—Calculus

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