Question 969027
Show without expanding that x = 2 is a root of the equation
<pre>
{{{abs(matrix(3,3,
 x,-6,-1,
2,-3x,x-3,  
-3,2x,x+2))}}}{{{""=""}}}{{{"0"}}} and solve it completely.

Substitute x=2 in the determinant

{{{abs(matrix(3,3,
 2,-6,-1,
2,-3(2),2-3,  
-3,2(2),2+2))}}}{{{""=""}}}{{{"0"}}}
 

{{{abs(matrix(3,3,
 2,-6,-1,
2,-6,-1,  
-3,4,4))}}}{{{""=""}}}{{{"0"}}}

The first two rows are the same, so if you subtract
the second row from the top row you get

{{{abs(matrix(3,3,
 0,0,0,
2,-6,-1,  
-3,4,4))}}}{{{""=""}}}{{{"0"}}}

If this were expanded about the top row, all the minors
would be multiplied by 0 giving 0.

Edwin</pre>