1MA0 Higher June 2013 Paper 1 Q18
18 Solve the simultaneous equations \[\begin{aligned} 4x + 7y &= 1 \\ 3x + 10y &= 15 \end{aligned}\] (4)
| Working | Answer | Mark | Notes |
|---|---|---|---|
| \(12x + 21y = 3\) \(12x + 40y = 60\) \(19y = 57\) \(y = 3\) \(3x + 10 \times 3 = 15\) \(3x = -15\) Alternative method \(x = \left(\frac{1 - 7y}{4}\right)\) \(3\left(\frac{1 - 7y}{4}\right) + 10y = 15\) \(3 - 21y + 40y = 60\) \(19y = 57\) \(x = \left(\frac{1 - 7 \times 3}{4}\right)\) | \(x = -5\), \(y = 3\) | 4 | M1 for a correct process to eliminate either \(x\) or \(y\) or rearrangement of one equation leading to substitution (condone one arithmetic error) A1 for either \(x = -5\) or \(y = 3\) M1 (dep) for correct substitution of their found value A1 cao |