4MA0 Higher June 2015 Paper 4 Q13
13 Solve \(3x^2 + 2x - 7 = 0\)
Give your solutions correct to 3 significant figures.
Show your working clearly.
(3)
| Scheme | Marks |
|---|---|
| \(\dfrac{-2 \pm \sqrt{2^2 - 4 \times 3 \times -7}}{2 \times 3}\) | M1 |
| \(\dfrac{-2 \pm \sqrt{4 + 84}}{6} = \dfrac{-2 \pm \sqrt{88}}{6}\) | M1 |
| 1.23, −1.90 | A1 |
| (3) |
Notes
M1: correct substitution into the quadratic formula, allow one sign error in numbers; some evaluation may be seen.
M1: Indep for simplification of discriminant to \(\sqrt{88}\) or \(\sqrt{4 + 84}\) or \(2\sqrt{22}\)
A1: 1.23 (or better), −1.90 (accept answers in range −1.90 to −1.89) provided at least M1 awarded