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1. anonymous

2. DanJS

2matrix multiplication , each term in the result is a dot product of the column vector and the row vector...

3. DanJS

here is the pattern a couple scrolls down http://www.mathsisfun.com/algebra/matrix-multiplying.html

4. anonymous

i got this answer

5. Michele_Laino

by definition of product between matrices, we get this: $\begin{gathered} \left( {\begin{array}{*{20}{c}} { - 1}&{ - 2} \\ 2&1 \end{array}} \right) \cdot \left( {\begin{array}{*{20}{c}} 3&1 \\ { - 1}&2 \end{array}} \right) = \hfill \\ \hfill \\ = \left( {\begin{array}{*{20}{c}} { - 1 \cdot 3 + \left( { - 2} \right) \cdot \left( { - 1} \right)}&{\left( { - 1} \right) \cdot 1 + \left( { - 2} \right) \cdot 2} \\ {2 \cdot 3 + 1 \cdot \left( { - 1} \right)}&{2 \cdot 1 + 1 \cdot 2} \end{array}} \right) \hfill \\ \end{gathered}$

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