Rational functions with parameters: finding parameter values from conditions

Questions where parameter values (a, b, λ, p) must be determined from given conditions such as known asymptotes, a point on the curve, or a given asymptote equation.

2 questions · Standard +0.3

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AQA Further AS Paper 1 2021 June Q16
8 marks Standard +0.3
16 Curve \(C\) has equation \(y = \frac { a x } { x + b }\) where \(a\) and \(b\) are constants.
The equations of the asymptotes to \(C\) are \(x = - 2\) and \(y = 3\) \includegraphics[max width=\textwidth, alt={}, center]{f7e7c21b-6e72-4c20-92fc-ba0336a11136-20_796_819_459_609} 16
  1. Write down the value of \(a\) and the value of \(b\) 16
  2. The gradient of \(C\) at the origin is \(\frac { 3 } { 2 }\) With reference to the graph, explain why there is exactly one root of the equation $$\frac { a x } { x + b } = \frac { 3 x } { 2 }$$ 16
  3. Using the values found in part (a), solve the inequality $$\frac { a x } { x + b } \leq 1 - x$$ [4 marks]
CAIE FP1 2019 November Q4
7 marks Standard +0.3
The line \(y = 2x + 1\) is an asymptote of the curve \(C\) with equation $$y = \frac{x^2 + 1}{ax + b}.$$
  1. Find the values of the constants \(a\) and \(b\). [3]
  2. State the equation of the other asymptote of \(C\). [1]
  3. Sketch \(C\). [Your sketch should indicate the coordinates of any points of intersection with the \(y\)-axis. You do not need to find the coordinates of any stationary points.] [3]