\Rightarrow \left[ {\begin{array}{*{20}c} a & 2a \\ { 0} & { a} \\ \end{array}} \right] + \left[ {\begin{array}{*{20}c} 0 & 0 \\ { -b} & { b} \\ \end{array}} \right] + \left[ {\begin{array}{*{20}c} 0 & 2c \\ { c} & { c} \\ \end{array}} \right]=\left[ {\begin{array}{*{20}c} 0 & 0 \\ { 0} & { 0} \\ \end{array}} \right] |