1MA0 Higher June 2015 Paper 2 Q20
20 Show that \((n + 3)^2 - (n - 3)^2\) is an even number for all positive integer values of \(n\). (3)
| Answer | Mark | Notes |
|---|---|---|
| Shown | 3 | M1 for correct expansion of \((n + 3)^2\) or \((n - 3)^2\) eg \((n + 3)^2 = n^2 + 6n + 9\) or \((n - 3)^2 = n^2 - 6n + 9\) M1 for correct expansion of complete expression, eg \((n^2 + 6n + 9) - (n^2 - 6n + 9)\) A1 for \(12n\) and conclusion OR M1 for \([n + 3 + n - 3][n + 3 - (n - 3)]\) M1 for \(2n \times 6\) A1 for conclusion |