Higher November 2020 Paper 1 Q12
12 Solve the simultaneous equations
\(7x - 2y = 34\)
\(3x + 5y = -3\)
Show clear algebraic working.
(4)
| Scheme | Marks |
|---|---|
Elimination E.g. \(21x - 6y = 102\) \(21x + 35y = -21\) \((-41y = 123)\) or \(35x - 10y = 170\) \(6x + 10y = -6\) \((41x = 164)\) or Substitution E.g. \(3\left(\dfrac{34 + 2y}{7}\right) + 5y = -3\) or \(3x + 5\left(\dfrac{7x - 34}{2}\right) = -3\) or \(7\left(\dfrac{-3 - 5y}{3}\right) - 2y = 34\) or \(7x - 2\left(\dfrac{-3 - 3x}{5}\right) = 34\) | M1 |
| A1 | |
| E.g. \(7x - 2 \times -3 = 34\) | M1 |
| Working required Answer: \(x = 4\) \(y = -3\) | A1 |
| (4) | |
| (4 marks) |
Notes
M1: for a correct method to eliminate \(x\) or \(y\): coefficients of \(x\) or \(y\) the same and correct operation to eliminate selected variable (condone 1 arithmetical error)
or
for correctly writing \(x\) or \(y\) in terms of the other variable and correctly substituting
A1: dep on M1 for \(x = 4\) or \(y = -3\)
M1: dep on M1 for substitution of found variable
or
repeating the steps in first M1 for the second variable
A1: cao
A correct answer without working scores no marks