User interface language: English | Español

Date May 2018 Marks available 2 Reference code 18M.1.SL.TZ2.S_10
Level Standard Level Paper Paper 1 Time zone Time zone 2
Command term Write down Question number S_10 Adapted from N/A

Question

Consider a function  f . The line L1 with equation  y = 3 x + 1  is a tangent to the graph of  f when  x = 2

Let  g ( x ) = f ( x 2 + 1 ) and P be the point on the graph of g where x = 1 .

Write down  f ( 2 ) .

[2]
a.i.

Find f ( 2 ) .

[2]
a.ii.

Show that the graph of g has a gradient of 6 at P.

[5]
b.

Let L2 be the tangent to the graph of g at P. L1 intersects L2 at the point Q.

Find the y-coordinate of Q.

[7]
c.

Markscheme

recognize that f ( x )  is the gradient of the tangent at x      (M1)

eg    f ( x ) = m

f ( 2 ) = 3   (accept m = 3)     A1 N2

[2 marks]

a.i.

recognize that  f ( 2 ) = y ( 2 )      (M1)

eg  f ( 2 ) = 3 × 2 + 1

f ( 2 ) = 7      A1 N2

[2 marks]

a.ii.

recognize that the gradient of the graph of g is  g ( x )       (M1)

choosing chain rule to find g ( x )       (M1)

eg   d y d u × d u d x , u = x 2 + 1 , u = 2 x

g ( x ) = f ( x 2 + 1 ) × 2 x      A2

g ( 1 ) = 3 × 2      A1

g ( 1 ) = 6      AG N0

[5 marks]

 

 

b.

 at Q, L1L2 (seen anywhere)      (M1)

recognize that the gradient of L2 is g'(1)  (seen anywhere)     (M1)
eg  m = 6

finding g (1)  (seen anywhere)      (A1)
eg   g ( 1 ) = f ( 2 ) , g ( 1 ) = 7

attempt to substitute gradient and/or coordinates into equation of a straight line      M1
eg   y g ( 1 ) = 6 ( x 1 ) , y 1 = g ( 1 ) ( x 7 ) , 7 = 6 ( 1 ) + b

correct equation for L2 

eg   y 7 = 6 ( x 1 ) , y = 6 x + 1      A1

correct working to find Q       (A1)
eg   same y-intercept,  3 x = 0

y = 1      A1 N2

[7 marks]

 

c.

Examiners report

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

Syllabus sections

Topic 5—Calculus » SL 5.4—Tangents and normal
Show 112 related questions
Topic 5—Calculus

View options