>> A = [1 2 3; 4 5 6; 7 8 0]

A =

     1     2     3
     4     5     6
     7     8     0

>> b = [0; 1; 2]

b =

     0
     1
     2

>> x = A\b

x =

    0.6667
   -0.3333
    0.0000

>> % Check
>> b - A*x

ans =

   1.0e-15 *

   -0.0740
   -0.2220
         0

>> % Enter a singular matrix.
>> C = A;
>> C(3,3) = 9

C =

     1     2     3
     4     5     6
     7     8     9

>> % Look at its reduced row echelon form to see that it is singular.
>> rref(C)

ans =

     1     0    -1
     0     1     2
     0     0     0

>> % Try solving a linear system with C as coefficient matrix.
>> C\b

Warning: Matrix is close to singular or badly scaled.
         Results may be inaccurate. RCOND = 2.055969e-18.

ans =

    1.6667
   -2.3333
    1.0000

>> % See if this is really a solution.
>> b - C*ans

ans =

   1.0e-15 *

         0
   -0.8882
         0

>> %  Looks ok.  Try a random right-hand side vector.
>> d = rand(3,1)

d =

    0.9501
    0.2311
    0.6068

>> C\d

Warning: Matrix is close to singular or badly scaled.
         Results may be inaccurate. RCOND = 2.055969e-18.

ans =

   1.0e+15 *

   -4.9301
    9.8601
   -4.9301

>> % This system has no solution.
>> exit

 629 flops.