June 2025 Paper 2 Q10
10 The first four terms of a quadratic sequence are
\(\qquad -1 \qquad 11 \qquad 31 \qquad 59\)
Work out an expression for the \(n\)th term.
Give your answer in the form \(\quad an^2 + b \quad\) where \(a\) and \(b\) are constants. [2 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(4n^2 - 5\) | B2 | B1 \(4n^2\ (\ldots)\) |
Additional guidance
| Accept \(4n^2 + -5\) | B2 |
| Answer \(a = 4 \quad b = -5\) | B2 |
| Answer \(a = 4 \quad b = 5\) | B1 |
| Accept \(\dfrac{8}{2}\) for 4 | |
| Condone eg \(4n^2 + 0n - 5\) | B2 |
| \(4n^2 + 4n - 5\) | B1 |
| Condone \(n\) being \(N\) or \(x\) etc for B2 or B1 | |
| \(n = 4n^2 - 5\) | B1 |
| \(n = 4n^2\) | B1 |