1MA0 Higher November 2015 Paper 1 Q21
21
(a) Write as a single fraction in its simplest form \(\dfrac{5}{2 - x} - \dfrac{4}{x}\) (3)
(b) Make \(y\) the subject of the formula \[t = \frac{2 - 3y}{y + 2}\] (4)
| Answer | Mark | Notes |
|---|---|---|
| \(\dfrac{9x - 8}{x(2 - x)}\) | 3 | M1 for method to use a common denominator, e.g. \(\dfrac{5(x) - 4(2 - x)}{x(2 - x)}\) M1 (dep on M1) for correct expansion of brackets and combination of numerators e.g. \(5x - 8 + 4x\) \((= 9x - 8)\) A1 for \(\dfrac{9x - 8}{x(2 - x)}\) or \(\dfrac{9x - 8}{2x - x^2}\) |
| Answer | Mark | Notes |
|---|---|---|
| \(y = \dfrac{2 - 2t}{t + 3}\) | 4 | M1 for intention to multiply both sides by \(y + 2\) as a first step e.g. \(t \times y + 2 = 2 - 3y\) M1 for intention to correctly isolate their \(y\) terms on one side and the other terms on the other side, e.g. \(ty + 3y = 2 - 2t\) M1 for intention to factorise, e.g. \(y(t + 3)\) \((= 2 - 2t)\) A1 for \(y = \dfrac{2 - 2t}{t + 3}\) oe |