Intermediate November 2021 Unit 2 Q17
17. Factorise \(x^2 - 4x - 12\), and hence solve \(x^2 - 4x - 12 = 0\). [3]
| Scheme | Marks | Comments |
|---|---|---|
| (x – 6)(x + 2) | B2 | B1 for (x ... 6)(x ... 2). |
| ( x =) 6 AND (x =) −2 | B1 | Strict F.T. from their brackets. Penalise change of letter −1. Allow the following. B2 for x − 6 (=0) AND x + 2 (=0) (B1) (x =) 6 AND ( x =) −2 (B1) B1 for x + 6 (=0) AND x − 2 (=0) (B0) ( x =) −6 AND (x =) 2 (B1) FT B1 if only (x =) 6 AND ( x =) −2 seen. (B1) Use of quadratic formula would only lead to this B1. Mark final answer. |