| Date | May 2012 | Marks available | 4 | Reference code | 12M.2.sl.TZ1.2 |
| Level | SL only | Paper | 2 | Time zone | TZ1 |
| Command term | Write down, Express, and Hence or otherwise | Question number | 2 | Adapted from | N/A |
Question
Let \(f(x) = 2{x^2} - 8x - 9\) .
(i) Write down the coordinates of the vertex.
(ii) Hence or otherwise, express the function in the form \(f(x) = 2{(x - h)^2} + k\) .
Solve the equation \(f(x) = 0\) .
Markscheme
(i) \((2{\text{, }} - 17)\) or \(x = 2\) , \(y = - 17\) A1A1 N2
(ii) evidence of valid approach (M1)
e.g. graph, completing the square, equating coefficients
\(f(x) = 2{(x - 2)^2} - 17\) A1 N2
[4 marks]
evidence of valid approach (M1)
e.g. graph, quadratic formula
\( - 0.9154759 \ldots \) , \(4.915475 \ldots \)
\(x = - 0.915\) , \(4.92\) A1A1 N3
[3 marks]
Examiners report
This question was well done by the majority of candidates.
This question was well done by the majority of candidates. There were still many however who opted for an analytical approach in part (b), which often led to errors in sign and accuracy. Some candidates used the trace feature on their GDC to find the vertex which often resulted in accuracy errors.
