Higher November 2023 Paper 3 Q20
20 Solve \(\quad 2x(x + 10) = 5x - 18\) [4 marks]
| Answer | Mark | Comments |
|---|---|---|
| \(2x^2 + 20x\) | M1 | |
| \(2x^2 + 20x - 5x + 18\ (= 0)\) or \(2x^2 + 15x + 18\ (= 0)\) or \(x^2 + 7.5x = -9\) | M1dep | oe |
| \((2x + 3)(x + 6)\) or \(\dfrac{-15 \pm \sqrt{15^2 - 4 \times 2 \times 18}}{2 \times 2}\) or \(-\dfrac{15}{4} \pm \sqrt{\dfrac{81}{16}}\) | M1 | oe eg \(\dfrac{-15 \pm \sqrt{81}}{4}\) correct factorisation or formula or completing the square for their 3-term quadratic |
| \(-6\) and \(-1.5\) | A1 | oe |
Additional guidance
| \(2x^2 + 10x - 5x - 18\) \(2x^2 + 5x - 18\) \((2x + 9)(x - 2)\) | M0M0M1A0 |