Write down the number of terms in this expansion.

Find the term containing \({x^2}\) .

12 terms     A1     N1

[1 mark]

evidence of binomial expansion     (M1)

e.g. \(\left( \begin{array}{l}
n\\
r
\end{array} \right){a^{n - r}}{b^r}\) , an attempt to expand, Pascal’s triangle

evidence of choosing correct term     (A1)

e.g. 10th term , \(r = 9\) , \(\left( {\begin{array}{*{20}{c}}
{11}\\
9
\end{array}} \right)\) , \({(x)^2}{(2)^9}\)

correct working     A1

e.g. \(\left( {\begin{array}{*{20}{c}}
{11}\\
9
\end{array}} \right){(x)^2}{(2)^9}\) , \(55 \times {2^9}\)

\(28160{x^2}\)     A1     N2

[4 marks]

Most candidates attempted this question, and many made good progress. A number of candidates spent time writing out Pascal’s triangle in full. Common errors included 11 for part (a) and not writing out the simplified form of the term for part (b). Another common error was adding instead of multiplying the parts of the term in part (b).

Most candidates attempted this question, and many made good progress. A number of candidates spent time writing out Pascal’s triangle in full. Common errors included 11 for part (a) and not writing out the simplified form of the term for part (b). Another common error was adding instead of multiplying the parts of the term in part (b).