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Date November 2019 Marks available 5 Reference code 19N.2.SL.TZ0.S_3
Level Standard Level Paper Paper 2 Time zone Time zone 0
Command term Find Question number S_3 Adapted from N/A

Question

Let  f ( x ) = x 8 ,   g ( x ) = x 4 3   and  h ( x ) = f ( g ( x ) ) .

Find h ( x ) .

[2]
a.

Let C be a point on the graph of h . The tangent to the graph of h at C is parallel to the graph of f .

Find the x -coordinate of C .

[5]
b.

Markscheme

attempt to form composite (in any order)        (M1)

eg        f ( x 4 3 ) ,   ( x 8 ) 4 3

h ( x ) = x 4 11        A1  N2

[2 marks]

a.

recognizing that the gradient of the tangent is the derivative        (M1)

eg        h

correct derivative (seen anywhere)        (A1)

h ( x ) = 4 x 3

correct value for gradient of f (seen anywhere)        (A1)

f ( x ) = 1 ,   m = 1

setting their derivative equal to 1         (M1)

4 x 3 = 1

0.629960

x = 1 4 3 (exact),  0.630        A1  N3

[5 marks]

b.

Examiners report

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

Syllabus sections

Topic 5 —Calculus » SL 5.3—Differentiating polynomials, n E Z
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Topic 5 —Calculus » SL 5.4—Tangents and normal
Topic 2—Functions » SL 2.5—Composite functions, identity, finding inverse
Topic 2—Functions
Topic 5 —Calculus

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