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Date November 2020 Marks available 2 Reference code 20N.1.SL.TZ0.S_3
Level Standard Level Paper Paper 1 Time zone Time zone 0
Command term Find Question number S_3 Adapted from N/A

Question

Let fx=12-2x, xa. The following diagram shows part of the graph of f.

The shaded region is enclosed by the graph of f, the x-axis and the y-axis.

The graph of f intersects the x-axis at the point a, 0.

Find the value of a.

[2]
a.

Find the volume of the solid formed when the shaded region is revolved 360° about the x-axis.

[5]
b.

Markscheme

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

recognize fx=0       (M1)

eg   12-2x=0,  2x=12 

a=6 (accept x=66, 0)    A1  N2

[2 marks] 

a.

attempt to substitute either their limits or the function into volume formula (must involve f2)      (M1)

eg   06f2dx , π12-2x2 , π0612-2xdx 

correct integration of each term      A1  A1

eg   12x-x2 , 12x-x2+c , 12x-x206

substituting limits into their integrated function and subtracting (in any order)      (M1)

eg    π126-62-π0 , 72π-36π , 126-62-0

 

Note: Award M0 if candidate has substituted into f, f2 or f'.

 

volume=36π      A1  N2      

[5 marks]

b.

Examiners report

[N/A]
a.
[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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