June 2025 Paper 1 Q2
2

The diagram shows the curve \(y = ax(x-b)\), where \(a\) and \(b\) are constants and \(b \gt 0\).
(a) Given that the curve has a stationary point at \(x = 3\), state the value of \(b\). [1]
(b) Given also that the stationary point at \(x = 3\) is a maximum, state what can be deduced about the value of \(a\). [1]
(c) Find the \(y\)-coordinate of the stationary point, giving your answer in terms of \(a\). [1]
(d) State the range of values of \(x\) for which the curve is increasing. [1]
| Scheme | Marks | AO |
|---|---|---|
| \((b =)\ 6\) | B1 | 2.2a |
| [1] |
| Scheme | Marks | AO |
|---|---|---|
| \(a \lt 0\) | B1 | 2.2a |
| [1] |
Notes
B1: oe in words eg \(a\) is negative
B0 for \(a \leqslant 0\)
B0 if left as \(2a \lt 0\)
| Scheme | Marks | AO |
|---|---|---|
| \((y =)\ -9a\) | B1 | 1.1 |
| [1] |
Notes
B1: Mark final answer, so B0 if \(-9a\) is then changed to \(9a\)
Must be given as a single term, not eg \(9a - 18a\)
| Scheme | Marks | AO |
|---|---|---|
| \(x \lt 3\) | B1 | 1.2 |
| [1] |
Notes
B1: Accept \(x \leqslant 3\)
oe in words
Do not penalise errors if set notation is attempted, as long as intention is clear