Intermediate November 2020 Unit 1 Q16
16.
(a) Factorise \(x^2 - 7x + 12\), and hence solve \(x^2 - 7x + 12 = 0\). [3]
(b) Expand and simplify \((5x - 2)^2\). [2]
| Scheme | Marks | Comments |
|---|---|---|
| \((x - 4)(x - 3)\) | B2 | B1 for (\(x\) ... 4)(\(x\) ... 3). Ignore ‘= 0’. |
| (\(x\) =) 4 AND (\(x\) =) 3 | B1 | Strict FT from their brackets. Allow the following. B2 for x − 4 (=0) AND x − 3 (=0) (B1) (x =) 4 AND ( x =) 3 (B1) B1 for x + 4 (=0) AND x + 3 (=0) (B0) ( x =) −4 AND (x =) −3 (B1) FT B1 if only (x =) 4 AND ( x =) 3 seen. (B1) |
| Scheme | Marks | Comments |
|---|---|---|
| \(25x^2 - 20x + 4\) | B2 | Otherwise B1 for sight of 25x2 ± kx + 4 (allow k = 0) B1 for sight of 25x2 − 20x − 4 Mark final answer. |