4400 Higher November 2010 Paper 4 Q18
18 Solve \(3x^2 + 8x + 2 = 0\)
Give your solutions correct to 3 significant figures.
(3)
| Scheme | Marks |
|---|---|
| \(\dfrac{-8 \pm \sqrt{8^2 - 4 \times 3 \times 2}}{2 \times 3}\) or for this expression with one or more of \(8^2\), \(4 \times 3 \times 2\) or \(2 \times 3\) correctly evaluated | M1 |
| obtains \(\sqrt{40}\) or \(\sqrt{64 - 24}\) or \(2\sqrt{10}\) or 6.32... | M1 |
| −0.279, −2.39 | A1 |
| (3) | |
| (3 marks) |
Notes
M1: for correct substitution
M1: (independent) for correct simplification of discriminant
A1: dep on both method marks for values rounding to −0.279 and −2.39 (−0.27924... , −2.38742...)