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Date May 2019 Marks available 2 Reference code 19M.1.SL.TZ2.S_10
Level Standard Level Paper Paper 1 (without calculator) Time zone Time zone 2
Command term Write down Question number S_10 Adapted from N/A

Question

Let  y = ( x 3 + x ) 3 2 .

Consider the functions  f ( x ) = x 3 + x and g ( x ) = 6 3 x 2 x 3 + x , for x ≥ 0.

The graphs of f and g are shown in the following diagram.

The shaded region R is enclosed by the graphs of f , g , the y -axis and x = 1 .

Hence find ( 3 x 2 + 1 ) x 3 + x d x .

[3]
b.

Write down an expression for the area of R .

[2]
c.

Hence find the exact area of R .

[6]
d.

Markscheme

integrating by inspection from (a) or by substitution       (M1)

eg   2 3 3 2 ( 3 x 2 + 1 ) x 3 + x d x u = x 3 + x d u d x = 3 x 2 + 1 , u 1 2 u 3 2 1.5

correct integrated expression in terms of x        A2 N3

eg    2 3 ( x 3 + x ) 3 2 + C ,   ( x 3 + x ) 1.5 1.5 + C

[3 marks]

 

 

b.

integrating and subtracting functions (in any order)        (M1)

eg    g f ,   f g

correct integral (including limits, accept absence of d x )       A1 N2

eg    0 1 ( g f ) d x ,   0 1 6 3 x 2 x 3 + x x 3 + x d x ,   0 1 g ( x ) 0 1 f ( x )

[2 marks]

c.

recognizing x 3 + x is a common factor (seen anywhere, may be seen in part (c))       (M1)

eg    ( 3 x 2 1 ) x 3 + x 6 ( 3 x 2 + 1 ) x 3 + x ,    ( 3 x 2 1 ) x 3 + x

correct integration      (A1)(A1)

eg    6 x 2 3 ( x 3 + x ) 3 2

Note: Award A1 for 6 x and award A1 for  2 3 ( x 3 + x ) 3 2 .

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

eg    6 2 3 ( 1 3 + 1 ) 3 2 ,   0 [ 6 2 3 ( 1 3 + 1 ) 3 2 ]

correct working       (A1)

eg    6 2 3 × 2 2 ,   6 2 3 × 4 × 2

area of  R = 6 4 2 3 ( = 6 2 3 8 , 6 2 3 × 2 3 2 , 18 4 2 3 )        A1  N3

[6 marks]

d.

Examiners report

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

Syllabus sections

Topic 5 —Calculus » SL 5.3—Differentiating polynomials, n E Z
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