June 2017 Paper 2 Q1
1
(a) The \(n\)th term of a sequence is \(\quad \dfrac{3 - 5n}{2}\)
Work out the difference between the 20th term and the 8th term. [2 marks]
(b) The \(n\)th term of another sequence is \(\quad \dfrac{3n}{1 - 2n}\)
Write down the limiting value of the sequence as \(n \to \infty\) [1 mark]
| Answer | Mark | Comments |
|---|---|---|
| \(\dfrac{3 - 5 \times 20}{2}\) or \(\dfrac{3 - 100}{2}\) or \((-)\dfrac{97}{2}\) or \((-)48.5\) or \(\dfrac{3 - 5 \times 8}{2}\) or \(\dfrac{3 - 40}{2}\) or \((-)\dfrac{37}{2}\) or \((-)18.5\) or \(12 \times (-)\dfrac{5}{2}\) | M1 | oe |
| \((-)30\) | A1 | Accept if both 30 and \(-30\) are seen |
| Answer | Mark | Comments |
|---|---|---|
| \(-\dfrac{3}{2}\) or \(-1\dfrac{1}{2}\) or \(-1.5\) | B1 | oe |
Additional guidance
| Condone \(\dfrac{3}{-2}\) or \(n \to -1.5\) or \(-1\dfrac{1}{2} \to \infty\) | B1 |
| \(-\dfrac{3\cancel{n}}{2\cancel{n}}\) | B1 |
| \(-\dfrac{3n}{2n}\) not processed | B0 |
| \(\dfrac{3}{0 - 2}\) not processed | B0 |
| \(-1.5n\) | B0 |