Higher June 2018 Paper 2 Q21
21. Use the method of completing the square to find the coordinates of the turning point of the curve \(y = x^2 + 12x + 57\). [4]
| Scheme | Marks | Comments |
|---|---|---|
| \((x+6)^2 \pm \ldots\) | B1 | Sight of \((x+6)^2\) or \((x + {}^{12}\!/_{2})^2\) Ignore sight of ‘=0’ |
| \(\ldots\ldots + 21\) | B1 | Accept 57 - 36 if not evaluated, otherwise mark final value. Do not accept ‘= -21’ or ‘=21’ \((x+6)^2 + 21\), B1, B1 ISW. |
| Stationary point (-6, 21) | B2 | Must follow completing the square FT from ‘their \((x+6)^2\)’ for the \(x\) coordinate FT their value but not 57 or - 36 for the \(y\) coordinate B1 for ( …. , 21) or (-6, ….) |
| (4) |