Question 985708
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  <TR>
  <TD>
{{{drawing( 101, 75, -0.5, 9.6, 1.0, 8.5,
            locate (0.4, 8.3, 3),
            locate (3.4, 8.3, 2),
            locate (6.6, 8.3, 7),
            locate (0.4, 5.9, 1),
            locate (3.4, 5.9, -2),
            locate (6.6, 5.9, 4),
            locate (0.4, 3.3, 5),
            locate (3.4, 3.3, 3),
            locate (6.6, 3.3, -1),

            arc (-1.0, 3.25, 22.0, 22.0, 330, 30),
            arc (10.4, 3.25, 22.0, 22.0, 150, 210),

        red(line (0.2, 7.5, 9.0, 7.5)),
        red(line (7.0, 7.2, 7.0, 0.0))
)}}}


<B>Figure</B>. The minor of the 
element equal 7 in the matrix

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The minor of the element equal &nbsp;7&nbsp; is the determinant of the &nbsp;2x2&nbsp; sub-matrix shown in the &nbsp;<B>Figure</B>. 


It is &nbsp;2x2&nbsp; sub-matrix &nbsp;{{{(matrix(2,2, 1, -2, 5, 3))}}}, &nbsp;and its determinant is &nbsp;1*3 - 5*(-2) = 3 + 10 = 13.


Thus the minor of the element equal &nbsp;7&nbsp; is &nbsp;13.


You can learn more from the lesson &nbsp;<A HREF=http://www.algebra.com/algebra/homework/Matrices-and-determiminant/Co-factoring-a-3x3-determinant.lesson>Co-factoring the determinant of a 3x3 matrix</A>&nbsp; in this site.