Find AB .

Given that ${\boldsymbol{X}} - 2{\boldsymbol{A}} = {\boldsymbol{B}}$, find X.

evidence of multiplying     (M1)

e.g. one correct element, $(0 \times - 4) + (3 \times 5)$

${\boldsymbol{AB}} = \left( {\begin{array}{*{20}{c}} {15}&3\\ {28}&4 \end{array}} \right)$     A2     N3

Note: Award A1 for three correct elements.

[3 marks]

finding $2{\boldsymbol{A}} = \left( {\begin{array}{*{20}{c}} 0&6\\ { - 4}&8 \end{array}} \right)$     (A1)

adding 2${\boldsymbol{A}}$ to both sides (may be seen first)     (M1)

e.g. ${\boldsymbol{X}} = {\boldsymbol{B}} +2{\boldsymbol{A}}$

 ${\boldsymbol{X}} = \left( {\begin{array}{*{20}{c}} { - 4}&6\\ 1&9 \end{array}} \right)$     A1     N2

[3 marks]

The large majority of candidates answered this question successfully. There were only a small number of candidates who seemed to have never worked with matrices before. Occasionally a candidate would incorrectly approach part (b) by finding an inverse of matrix A.

The large majority of candidates answered this question successfully. There were only a small number of candidates who seemed to have never worked with matrices before. Occasionally a candidate would incorrectly approach part (b) by finding an inverse of matrix A.