Specimen 2020 Paper 1 Q3
3
\[3a(2x - 1) + 4(ax + 5) \equiv 60x + b\]Work out the values of \(a\) and \(b\). [4 marks]
| Answer | Mark | Comments |
|---|---|---|
| Alternative method 1 | ||
| \(6ax - 3a + 4ax + 20\) | M1 | both brackets expanded correctly |
| \(6a + 4a = 60\) or \(-3a + 20 = b\) | M1 | either coefficient equated correctly |
| \(a = 6\) | A1 | |
| \(b = 2\) | A1 | |
| Alternative method 2 | ||
| Correct substitutions leading to two correct equations in \(a\) and \(b\) | M1 | |
| A correct attempt to eliminate either \(a\) or \(b\) | M1 | any valid method |
| \(a = 6\) | A1 | |
| \(b = 2\) | A1 | |