Question 636414
Since the first matrix is a <font color="red">2</font> by 2 matrix and the second matrix is a 2 by <font color="green">2</font> matrix, this means that the resulting matrix will be a <font color="red">2</font> by <font color="green">2</font> matrix. The final matrix will have the same number of rows as the first matrix and the same number of columns as the second matrix.<br>

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  So the final resulting matrix will look like:<br>
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  <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2Cx%2Cx%2Cx%2Cx%29%29&amp;x=0003" alt="%28matrix%282%2C2%2Cx%2Cx%2Cx%2Cx%29%29" align="MIDDLE"><br>
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  note: the "x"s are just placeholders for now<br>
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  <br><br>--------------------------------------------------<br><br><br><br><br><br>Multiply the corresponding entries from the <font size="4" color="red">1st</font> row of the first matrix by the <font size="4" color="green">1st</font> column of the second matrix. After multiplying, add the values:<br><br><br><br><font size="4" color="red">1st</font> row, <font size="4" color="green">1st</font> column: <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2Chighlight%282%29%2Chighlight%283%29%2C1%2C4%29%29%28matrix%282%2C2%2Chighlight%280%29%2C-2%2Chighlight%281%29%2C5%29%29&amp;x=0003" alt="%28matrix%282%2C2%2Chighlight%282%29%2Chighlight%283%29%2C1%2C4%29%29%28matrix%282%2C2%2Chighlight%280%29%2C-2%2Chighlight%281%29%2C5%29%29" align="MIDDLE"><br><br><img src="/cgi-bin/plot-formula.mpl?expression=%282%29%2A%280%29%2B%283%29%2A%281%29=0%2B3=3&amp;x=0003" alt="%282%29%2A%280%29%2B%283%29%2A%281%29=0%2B3=3" align="MIDDLE"><br><br><br><br> So the element in the <font size="4" color="red">1st</font> row, <font size="4" color="green">1st</font> column of the resulting matrix is <img src="/cgi-bin/plot-formula.mpl?expression=3&amp;x=0003" alt="3" align="MIDDLE">. Now let's update the matrix:<br><br> <br><br><img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C3%2Cx%2Cx%2Cx%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C3%2Cx%2Cx%2Cx%29%29" align="MIDDLE"><br><br>--------------------------------------------------<br><br><br><br><br><br>Multiply the corresponding entries from the <font size="4" color="red">1st</font> row of the first matrix by the <font size="4" color="green">2nd</font> column of the second matrix. After multiplying, add the values:<br><br><br><br><font size="4" color="red">1st</font> row, <font size="4" color="green">2nd</font> column: <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2Chighlight%282%29%2Chighlight%283%29%2C1%2C4%29%29%28matrix%282%2C2%2C0%2Chighlight%28-2%29%2C1%2Chighlight%285%29%29%29&amp;x=0003" alt="%28matrix%282%2C2%2Chighlight%282%29%2Chighlight%283%29%2C1%2C4%29%29%28matrix%282%2C2%2C0%2Chighlight%28-2%29%2C1%2Chighlight%285%29%29%29" align="MIDDLE"><br><br><img src="/cgi-bin/plot-formula.mpl?expression=%282%29%2A%28-2%29%2B%283%29%2A%285%29=-4%2B15=11&amp;x=0003" alt="%282%29%2A%28-2%29%2B%283%29%2A%285%29=-4%2B15=11" align="MIDDLE"><br><br><br><br> So the element in the <font size="4" color="red">1st</font> row, <font size="4" color="green">2nd</font> column of the resulting matrix is <img src="/cgi-bin/plot-formula.mpl?expression=11&amp;x=0003" alt="11" align="MIDDLE">. Now let's update the matrix:<br><br> <br><br><img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C3%2C11%2Cx%2Cx%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C3%2C11%2Cx%2Cx%29%29" align="MIDDLE"><br><br><br><br><br><br>================================================================================<br><br><br><br><br><br>Multiply the corresponding entries from the <font size="4" color="red">2nd</font> row of the first matrix by the <font size="4" color="green">1st</font> column of the second matrix. After multiplying, add the values:<br><br><br><br><font size="4" color="red">2nd</font> row, <font size="4" color="green">1st</font> column: <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C2%2C3%2Chighlight%281%29%2Chighlight%284%29%29%29%28matrix%282%2C2%2Chighlight%280%29%2C-2%2Chighlight%281%29%2C5%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C2%2C3%2Chighlight%281%29%2Chighlight%284%29%29%29%28matrix%282%2C2%2Chighlight%280%29%2C-2%2Chighlight%281%29%2C5%29%29" align="MIDDLE"><br><br><img src="/cgi-bin/plot-formula.mpl?expression=%281%29%2A%280%29%2B%284%29%2A%281%29=0%2B4=4&amp;x=0003" alt="%281%29%2A%280%29%2B%284%29%2A%281%29=0%2B4=4" align="MIDDLE"><br><br><br><br> So the element in the <font size="4" color="red">2nd</font> row, <font size="4" color="green">1st</font> column of the resulting matrix is <img src="/cgi-bin/plot-formula.mpl?expression=4&amp;x=0003" alt="4" align="MIDDLE">. Now let's update the matrix:<br><br> <br><br><img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C3%2C11%2C4%2Cx%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C3%2C11%2C4%2Cx%29%29" align="MIDDLE"><br><br>--------------------------------------------------<br><br><br><br><br><br>Multiply the corresponding entries from the <font size="4" color="red">2nd</font> row of the first matrix by the <font size="4" color="green">2nd</font> column of the second matrix. After multiplying, add the values:<br><br><br><br><font size="4" color="red">2nd</font> row, <font size="4" color="green">2nd</font> column: <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C2%2C3%2Chighlight%281%29%2Chighlight%284%29%29%29%28matrix%282%2C2%2C0%2Chighlight%28-2%29%2C1%2Chighlight%285%29%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C2%2C3%2Chighlight%281%29%2Chighlight%284%29%29%29%28matrix%282%2C2%2C0%2Chighlight%28-2%29%2C1%2Chighlight%285%29%29%29" align="MIDDLE"><br><br><img src="/cgi-bin/plot-formula.mpl?expression=%281%29%2A%28-2%29%2B%284%29%2A%285%29=-2%2B20=18&amp;x=0003" alt="%281%29%2A%28-2%29%2B%284%29%2A%285%29=-2%2B20=18" align="MIDDLE"><br><br><br><br> So the element in the <font size="4" color="red">2nd</font> row, <font size="4" color="green">2nd</font> column of the resulting matrix is <img src="/cgi-bin/plot-formula.mpl?expression=18&amp;x=0003" alt="18" align="MIDDLE">. Now let's update the matrix:<br><br> <br><br><img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C3%2C11%2C4%2C18%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C3%2C11%2C4%2C18%29%29" align="MIDDLE"><br><br><br><br><br><br><br><br><br><br>==============================================================================<br><br><br><br>Answer:<br><br><br><br>So the solution is  <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C3%2C11%2C4%2C18%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C3%2C11%2C4%2C18%29%29" align="MIDDLE"><br>

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  In other words,<br>
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  <img src="/cgi-bin/plot-formula.mpl?expression=%28matrix%282%2C2%2C2%2C3%2C1%2C4%29%29%2A%28matrix%282%2C2%2C0%2C-2%2C1%2C5%29%29=%28matrix%282%2C2%2C3%2C11%2C4%2C18%29%29&amp;x=0003" alt="%28matrix%282%2C2%2C2%2C3%2C1%2C4%29%29%2A%28matrix%282%2C2%2C0%2C-2%2C1%2C5%29%29=%28matrix%282%2C2%2C3%2C11%2C4%2C18%29%29" align="MIDDLE"><br>
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