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Date May 2008 Marks available 5 Reference code 08M.2.hl.TZ2.8
Level HL only Paper 2 Time zone TZ2
Command term Sketch Question number 8 Adapted from N/A

Question

The graph of \(y = f(x){\text{ for }} - 2 \leqslant x \leqslant 8\) is shown.

 

 

On the set of axes provided, sketch the graph of \(y = \frac{1}{{f(x)}}\), clearly showing any asymptotes and indicating the coordinates of any local maxima or minima.

 

Markscheme

     A1A1A1A1A1

 

Notes: Award A1 for vertical asymptotes at x = −1, x = 2 and x = 5 .

A1 for \(x \to - 2,{\text{ }}\frac{1}{{f(x)}} \to {0^ + }\)

A1 for \(x \to 8,{\text{ }}\frac{1}{{f(x)}} \to - 1\)

A1 for local maximum at \(\left( {0, - \frac{1}{2}} \right)\) (branch containing local max. must be present)

A1 for local minimum at (3, 1) (branch containing local min. must be present)

In each branch, correct asymptotic behaviour must be displayed to obtain the A1.

Disregard any stated horizontal asymptotes such as y = 0 or y = −1 .

 

[5 marks]

Examiners report

A large number of candidates had difficulty graphing the reciprocal function. Most candidates were able to locate the vertical asymptotes but experienced difficulties graphing the four constituent branches. A common error was to specify incorrect coordinates of the local maximum i.e. (0,–1) or (0,–2) instead of \(\left( {0, - \frac{1}{2}} \right)\). A few candidates attempted to sketch the inverse while others had difficulty using the scaled grid.

Syllabus sections

Topic 2 - Core: Functions and equations » 2.2 » The graph of \(\frac{1}{{f\left( x \right)}}\) given the graph of \(y = f(x)\) .

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