Date | May 2012 | Marks available | 7 | Reference code | 12M.2.hl.TZ1.9 |
Level | HL only | Paper | 2 | Time zone | TZ1 |
Command term | Find | Question number | 9 | Adapted from | N/A |
Question
Find the constant term in the expansion of \({\left( {x - \frac{2}{x}} \right)^4}{\left( {{x^2} + \frac{2}{x}} \right)^3}\).
Markscheme
\({\left( {x - \frac{2}{x}} \right)^4} = {x^4} - 8{x^2} + 24 - \frac{{32}}{{{x^2}}} + \frac{{16}}{{{x^4}}}\) (M1)(A1)
\({\left( {{x^2} + \frac{2}{x}} \right)^3} = {x^6} + 6{x^3} + 12 + \frac{8}{{{x^3}}}\) (M1)(A1)
Note: Accept unsimplified or uncalculated coefficients in the constant term
\( = 24 \times 12\) (M1)(A1)
\( = 288\) A1
[7 marks]
Examiners report
Many correct answers were seen, although most candidates used rather inefficient methods (e.g. expanding the brackets in multiple steps). In a very few cases candidates used the binomial theorem to obtain the answer quickly.