June 2023 Paper 1 Q19
19 \(\quad 8x^2 + 20x + n \equiv c(x + d)^2 + 3 \quad\) where \(c\), \(d\) and \(n\) are constants.
Work out the values of \(c\), \(d\) and \(n\). [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| (\(c =\)) 8, (\(d =\)) \(\dfrac{5}{4}\) or 1.25 and (\(n =\)) \(\dfrac{31}{2}\) or \(15\dfrac{1}{2}\) or 15.5 | B3 | oe B2 any 2 correct on answer line (not embedded) B1 (\(d =\)) \(\dfrac{5}{4}\) or 1.25 or (\(n =\)) \(\dfrac{31}{2}\) or \(15\dfrac{1}{2}\) or 15.5 on answer line or \(cx^2 + 2cdx + cd^2\) (+3) or \(8\left(x + \dfrac{5}{4}\right)^2\) or \(8(x + 1.25)^2\) in method |
Additional guidance
| (\(c =\)) 8 on its own is 0 marks | M0 A0 |