IB DP Maths Topic 2.5 Vertical and horizontal asymptotes SL Paper 1

Question

Let \(f(x) = p + \frac{9}{{x – q}}\), for \(x \ne q\). The line \(x = 3\) is a vertical asymptote to the graph of \(f\).

Write down the value of \(q\).

[1]
a.

The graph of \(f\) has a \(y\)-intercept at \((0,{\text{ }}4)\).

Find the value of \(p\).

[4]
b.

The graph of \(f\) has a \(y\)-intercept at \((0,{\text{ }}4)\).

Write down the equation of the horizontal asymptote of the graph of \(f\).

[1]
c.
Answer/Explanation

Markscheme

\(q = 3\)     A1     N1

[1 mark]

a.

correct expression for \(f(0)\)     (A1)

eg\(\;\;\;p + \frac{9}{{0 – 3}},{\text{ }}4 = p + \frac{9}{{ – q}}\)

recognizing that \(f(0) = 4\;\;\;\)(may be seen in equation)     (M1)

correct working     (A1)

eg\(\;\;\;4 = p – 3\)

\(p = 7\)     A1     N3

[3 marks]

b.

\(y = 7\;\;\;\)(must be an equation, do not accept \(p = 7\)     A1     N1

[1 mark]

Total [6 marks]

c.
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