Higher November 2017 Paper 4 Q18
18 Solve this equation algebraically.
Give your solutions correct to 2 decimal places.
| Answer | Marks | Part marks and guidance | |
|---|---|---|---|
| −1.85 [0].18 | 4 | M2 for \(\dfrac{-5 \pm \sqrt{5^2 - 4 \times 3 \times -1}}{2 \times 3}\) or better and condone one error or M1 for the formula with at most two errors and A1 for −1.85 or [0].18 or for both answers correct but to more than 2dp. e.g. 0.180... and −1.847… | Accept any correct algebraic method e.g. completing the square \(3\left[x^2 + \frac{5}{3}x - \frac{1}{3}\right] = 0\) \(3\left[\left(x + \frac{5}{6}\right)^2 - \frac{37}{36}\right] = 0\) |
Notes
(corrected from the printed mark scheme: the completing-the-square example is printed as \(3\left[x^2 + \frac{5}{3}x + \frac{1}{3}\right] = 0\) and \(3\left[\left(x + \frac{5}{6}\right)^2 - \frac{13}{36}\right] = 0\))