0004.ptx

<exercise checkit-seed="0004" checkit-slug="M1" checkit-title="Multiplying matrices">
  <statement>
    <p>Of the following three matrices, only two may be multiplied.
      <me>
          A= \left[\begin{array}{ccc}
2 &amp; -1 &amp; -1 \\
1 &amp; 0 &amp; -2 \\
3 &amp; -1 &amp; -2 \\
2 &amp; -1 &amp; -1
\end{array}\right]  \hspace{1em} B= \left[\begin{array}{cc}
3 &amp; 3 \\
0 &amp; 1 \\
-2 &amp; -2 \\
1 &amp; 0
\end{array}\right]  \hspace{1em} C= \left[\begin{array}{ccc}
3 &amp; 5 &amp; -3 \\
1 &amp; 2 &amp; -1
\end{array}\right] </me>
      Explain which two can be multiplied and why. Then show how to find their product.</p>
  </statement>
  <answer>
    <me>BC= \left[\begin{array}{ccc}
12 &amp; 21 &amp; -12 \\
1 &amp; 2 &amp; -1 \\
-8 &amp; -14 &amp; 8 \\
3 &amp; 5 &amp; -3
\end{array}\right] </me>
  </answer>
</exercise>