Foundation November 2023 Paper 3 Q26
26 The area of this rectangle can be written as \(ax^2 + bx - 10\).
Not to scale
Find the values of \(a\), \(b\) and \(c\).
You must show your working. [5]
| Answer | Marks | Part marks and guidance | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| \(a = 3\), \(b = -13\), \(c = -5\) with correct working | 5 | M1 for \((3x + 2)(x + c)\) soi B1 for \(a = 3\) B1 for \(c = -5\) AND M1 for \(3c + 2\) or \(3 \times\) their \(c\) \(+ 2\) either alone or as coefficients of \(x\) in a full or partial expansion B1 for \(b = -13\) | Correct working requires evidence of at least one M1 Condone \(3x + 2 \times x + c\) as soi Grid method for expanding e.g.
M1 for shaded cells correct Accept \(x(3c + 2)\) and \(3cx + 2x\) ignore coefficient of \(x^2\) and constant Condone embedded answers for b or c provided they are not then contradicted on answer line eg. B1 for \((x - 5)\) and B1 for \(-13x\) seen | |||||||||