## Exam-Style Questions on Functions## Problems on Functions adapted from questions set in previous exams. |

## 1. | GCSE Higher |

\(f(x) = \frac{2x}{5} + 7\) and \(g(x) = 10x^2 - 15\) for all values of \(x\).

Find \(fg(x)\).

Give your answer in the form \(ax^2 + b\) where \(a\) and \(b\) are integers.

## 2. | IGCSE Extended |

The table shows some values (rounded to one decimal place) for the function \(y=\frac{2}{x^2}-x, x\neq 0\).

\(x\) | -3 | -2 | -1 | -0.5 | 0.5 | 1 | 2 | 3 | 4 |
---|---|---|---|---|---|---|---|---|---|

\(y\) | 3.2 | 2.5 | 8.5 | 7.5 | 1.0 | -2.8 |

(a) Complete the table of values.

(b) Draw the graph of \(y=\frac{2}{x^2}-x\) for \(-3\le x \le -0.5\) and \(0.5\le x\le 4\).

(c) Use your graph to solve the equation \(\frac{2}{x^2}-x-3=0\)

(d) Use your graph to solve the equation \(\frac{2}{x^2}-x=1-2x\)

(e) By drawing a suitable tangent, find an estimate of the gradient of the curve at the point where x = 1.

(f) Using algebra, show that you can use the graph at \(y=0\) to find \(\sqrt[3]2\)

## 3. | GCSE Higher |

(a) A function is represented by the following function machine.

A number is input into the machine and the output is used as a new input.

If the second output is 53 work out the number that was the first input.

(b) A number is input into the machine and the output produced is the same number. Work out what this number could have been.

(c) Another function machine is shown below.

If the Input is 2, the Output is 7.

If the Input is 6, the Output is 27.

Use this information to fill in the two boxes.

## 4. | IB Standard |

The Big Wheel at Fantasy Fun Fayre rotates clockwise at a constant speed completing 15 rotations every hour. The wheel has a diameter of 90 metres and the bottom of the wheel is 6 metres above the ground.

A cabin starts at the bottom of the wheel with the top of the cabin 6m above the ground.

(a) Find the greatest height of the top of the cabin reaches as the wheel rotates.

After \(t\) minutes, the height \(h(t)\) metres above the ground of the top of a cabin is given by the function \(h(t)=51-a\cos bt\).

(b) Find the period of \(h(t)\)

(c) Find the value of \(b\).

(d) Find the value of \(a\).

(e) Sketch the graph of \(h(t)\) , for \(0\le t\le 5\).

(f) In one rotation of the wheel, find the probability that a randomly selected seat is at least 70 metres above the ground. Give your answer to two decimal places.

## 5. | IB Standard |

Let \(f (x)=a(x-b)^2+c\). The vertex of the graph of \(f\) is at (4, -3) and the graph passes through (3, 2).

(a) Find the value of \(c\).

(b) Find the value of \(b\).

(c) Find the value of \(a\).

## 6. | IB Standard |

The population of sheep on a ranch is modelled by the function \(P(t)= 65 \sin(0.4t-3.2)+450\), where t is in months, and \(t=1\) corresponds to 1st January 2015.

(a) Find the number of sheep on the ranch on 1st July 2015.

(b) Find the rate of change of the sheep population on 1st July 2015.

(c) Explain your answer to part (b) with reference to the sheep population size on 1st July2015.

## 7. | IB Standard |

The diagram shows the graph of \(y=f(x)\), for \(-3\le x \le 4\).

The graph passes through the point (4,0.65).

(a) Find the value of \(f(-2)\);

(b) Find the value of \(f^{-1}(0)\);

(c) Find the domain of \(f^{-1}\).

(d) Sketch the graph of \(f^{-1}\).

## 8. | IGCSE Extended |

If \(f(x)=5-4x\) and \(g(x)=4^{-x}\) then:

(a) Find \(f(3x)\) in terms of \(x\).

(b) Find \(ff(x)\) in its simplest form.

(c) Work out \(gg(–1)\) give your answer as a fraction.

(d) Find \(f^{–1}(x)\), the inverse of \(f(x)\).

(e) Solve the equation \(gf(x)= 1\).

## 9. | GCSE Higher |

Here is a function machine that produces two outputs, A and B.

Work out the range of input values for which the output A is less than the output B.

## 10. | IB Standard |

The diagram shows part of the graph of \(f(x)=Ae^{kx}+2\).

The y-intercept is at \((0,10)\).

(a) Show that \(A=8\).

(b) Given that \(f(8)=3.62\) (correct to 3 significant figures), find the value of \(k\).

(c) (i) Using your value of \(k\), find \(f'(x)\).

(ii) Hence, explain why \(f\) is a decreasing function.

(iii) Find the equation of the horizontal asymptote of the graph \(f\).

Let \(g(x)=-x^2+7x+5\)

(d) Find the area enclosed by the graphs of \(f\) and \(g\).

## 11. | IB Standard |

Let \(f(x)=\sin ( \frac {\pi}{4}x) + \cos ( \frac {\pi}{4}x) \), for \(-4\le x \le 4\)

(a) Sketch the graph of \(f\).

(b) Find the values of \(x\) where the function is decreasing.

(c) The function \(f\) can also be written in the form \(f(x)=a\sin ( \frac {\pi}{4}(x+c))\) where \(a\in \mathbf R\) and \(0 \le c \le 2\). Find the value of \(a\) and \(c\).

## 12. | IB Studies |

The cross-section of a fish pond is drawn on a set of axes shown below. The edge is modelled by \(y=ax^2+c\) and the cross section is the same for the whole of its length. The curve touches the x-axis at the origin.

Point A has coordinates (-9,5.4) and point B has coordinates (9,5.4).

(a) Find the value of \(c\).

(b) Find the value of \(a\).

(c) Hence write down the equation of the quadratic function which models the edge of the fish pond.

(d) Calculate the value of \(y\) when \(x\)=7.2m.

(e) State what the value of \(x\) and the value of \(y\) represent for this fish pond.

(f) Find the value of \(x\) when the height of water in the pond is 2.7m.

The pond is filled to a maximum depth of 2.7m and the the cross-sectional area of the water is 22.9m^{2}. The pond has a length of 8m.

(g) Calculate the volume of water in the pond.

## 13. | IB Standard |

The diagram shows part of the graph of \(y=asinbx+c\) with a minimum at \((-2.5,-2)\) and a maximum at \((2.5,4)\).

(a) Find \(a\).

(b) Find \(b\).

(c) Find \(c\).

## 14. | IB Standard |

Let \(f(x)=5x^2-20x+k\). The equation \(f(x)=0\) has two equal roots.

(a) Write down the value of the discriminant.

(b) Hence, show that \(k=20\).

The graph of \(f\) has its vertex on the x-axis.

(c) Find the coordinates of the vertex of the graph of \(f\).

(d) Write down the solution of \(f(x)=0\).

The function can be written in the form \(f(x)=a(x-h)^2+j\).

(e) Find the value of \(a\).

(f) Find the value of \(h\).

(g) Find the value of \(j\).

(h) The graph of a function \(g\) is obtained from the graph of \(f\) by a reflection in the x-axis, followed by a translation by the vector \(\begin{pmatrix} 0 \\ 3 \\ \end{pmatrix} \). Find \(g\), giving your answer in the form \(g(x)=Ax^2+Bx+C\).

## 15. | IB Standard |

Consider the graph of \(f(x)=a\sin(b(x+c))+12\), for \(0\le x\le 24\).

The graph has a maximum at (8, 22) and a minimum at (18, 2).

(a) Find the value of \(a\).

(b) Find the value of \(b\).

(c) Find the value of \(c\).

(d) Solve \(f(x)=5\).

The exam-style questions appearing on this site are based on those set in previous examinations (or sample assessment papers for future examinations) by the major examination boards. The wording, diagrams and figures used in these questions have been changed from the originals so that students can have fresh, relevant problem solving practice even if they have previously worked through the related exam paper.

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