Higher January 2021 Paper 2R Q12
12 Solve the simultaneous equations \(\begin{aligned} 2x + 7y &= 17 \\ 5x + 3y &= -1 \end{aligned}\)
Show clear algebraic working.
(4)
| Scheme | Marks |
|---|---|
eg. \(10x + 35y = 85\) \(\phantom{eg.\ }10x + 6y = -2\) with the operation of subtraction or \(29y = 87\) or \(6x + 21y = 51\) \(\phantom{or\ }35x + 21y = -7\) with the operation of subtraction or \(29x = -58\) or eg \(5\left(\dfrac{17 - 7y}{2}\right) + 3y = -1\) or eg \(5x + 3\left(\dfrac{17 - 2x}{7}\right) = -1\) | M1 |
| M1 | |
| Working required Answer: \(x = -2\) | A1 |
| \(y = 3\) | A1 |
| (4) | |
| (4 marks) |
Notes
M1: for correct method to eliminate one variable – multiplying one or both equations so the coefficient of x or y is the same in both, with the correct operation to eliminate one variable (condone one arithmetic error)
or isolating x or y in one equation and substituting into the other (condone one arithmetic error).
M1: dep 1st M1 Substitute found value into one equation or correct method to eliminate second unknown.
A1: dep 1st M1