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2.8 Reciprocal and simple rational functionsIB Maths: Analysis and Approaches HL: Subtopic test

10 questions, 27 marks

IB Maths: Analysis and Approaches HL

2.8 Reciprocal and simple rational functions

Total 27 marks

Name

Class

Date

  1. 1
    The function ff is defined by f(x)=3x−6x+2f(x) = \dfrac{3x - 6}{x + 2}, x∈Rx \in \mathbb{R}, x≠−2x \ne -2.
    (a)
    Write down the equation of the vertical asymptote of the graph of ff.
    [1 mark]
    • Ax=2x = 2
    • Bx=−2x = -2
    • Cx=3x = 3
    • Dy=−2y = -2
    (b)
    Write down the equation of the horizontal asymptote of the graph of ff.
    [1 mark]
    • Ay=−3y = -3
    • By=13y = \frac{1}{3}
    • Cy=0y = 0
    • Dy=3y = 3
    (c)
    Find the coordinates of the points where the graph of ff meets the xx-axis and the yy-axis.
    [2 marks]

    Total for question 1: 4 marks

  2. 2
    Let h(x)=1xh(x) = \dfrac{1}{x}, x∈Rx \in \mathbb{R}, x≠0x \ne 0.
    (a)
    Find the value of (h∘h)(5)(h \circ h)(5).
    [1 mark]
    • A55
    • B125\frac{1}{25}
    • C15\frac{1}{5}
    • D2525
    (b)
    The point (14,4)\left(\frac{1}{4}, 4\right) lies on the graph of y=h(x)y = h(x). Which other point must also lie on the graph, because hh is its own inverse?
    [1 mark]
    • A(−14,4)\left(-\frac{1}{4}, 4\right)
    • B(14,−4)\left(\frac{1}{4}, -4\right)
    • C(4,14)\left(4, \frac{1}{4}\right)
    • D(4,4)(4, 4)
    (c)
    Find the coordinates of the points where the graph of y=h(x)y = h(x) meets the line y=4xy = 4x.
    [2 marks]

    Total for question 2: 4 marks

  3. 3
    A student practises touch-typing. After tt hours of practice, the student's typing speed, WW words per minute, is modelled by W(t)=60t+20t+2W(t) = \dfrac{60t + 20}{t + 2}, t≥0t \ge 0.
    (a)
    Find the number of hours of practice after which the model predicts a speed of 45 words per minute.
    [3 marks]
    (b)
    (i) Show that W(t)=60−100t+2W(t) = 60 - \dfrac{100}{t + 2}.
    (ii) Hence write down the equation of the horizontal asymptote of the graph of
    WW, and interpret it in the context of the model.
    [4 marks]

    Total for question 3: 7 marks

  4. 4
    The function ff is defined by f(x)=ax+12x−bf(x) = \dfrac{ax + 1}{2x - b}, x≠b2x \ne \frac{b}{2}, where a,b∈Ra, b \in \mathbb{R}. The graph of ff has a vertical asymptote x=3x = 3 and a horizontal asymptote y=−2y = -2.
    (a)
    (i) Find the value of aa and the value of bb.
    (ii) Find the coordinates of the points where the graph of
    ff meets the axes.
    [6 marks]
    (b)
    (i) Find an expression for f−1(x)f^{-1}(x) and state its domain.
    (ii) Write down the equations of the asymptotes of the graph of
    y=f−1(x)y = f^{-1}(x), and explain how they are related to the asymptotes of the graph of ff.
    [6 marks]

    Total for question 4: 12 marks

End of questions