>> A = [1 -1 0 0 50; 1 0 0 1 870; 0 1 -1 0 -120; 0 0 1 0 350]

A =

     1    -1     0     0    50
     1     0     0     1   870
     0     1    -1     0  -120
     0     0     1     0   350

>> rref(A)

ans =

     1     0     0     0   280
     0     1     0     0   230
     0     0     1     0   350
     0     0     0     1   590


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

A =

     1     2     3
     4     5     6

>> B = [2 1 3; 5 1 7]

B =

     2     1     3
     5     1     7

>> A + B

ans =

     3     3     6
     9     6    13

>> 5 * A

ans =

     5    10    15
    20    25    30

>> C = B'

C =

     2     5
     1     1
     3     7

>> A * C

ans =

    13    28
    31    67

>> A * C
??? Error using ==> *
Inner matrix dimensions must agree.

>> A = [1 2; 3 4]

A =

     1     2
     3     4

>> inv(A)

ans =

   -2.0000    1.0000
    1.5000   -0.5000

>> A = [ 1 2 ; 2 4]

A =

     1     2
     2     4

>> inv(A)
Warning: Matrix is singular to working precision.

ans =

   Inf   Inf
   Inf   Inf

>> quit