A = rand(3)
A =
      0.81472      0.91338       0.2785
      0.90579      0.63236      0.54688
      0.12699      0.09754      0.95751
diag(A)
ans =
      0.81472
      0.63236
      0.95751
B = rand(2,3)
B =
      0.96489      0.97059      0.48538
      0.15761      0.95717      0.80028
diag(B)
ans =
      0.96489
      0.95717
eye(3)
ans =
     1     0     0
     0     1     0
     0     0     1
eye(9)
ans =
     1     0     0     0     0     0     0     0     0
     0     1     0     0     0     0     0     0     0
     0     0     1     0     0     0     0     0     0
     0     0     0     1     0     0     0     0     0
     0     0     0     0     1     0     0     0     0
     0     0     0     0     0     1     0     0     0
     0     0     0     0     0     0     1     0     0
     0     0     0     0     0     0     0     1     0
     0     0     0     0     0     0     0     0     1
eye(3)
ans =
     1     0     0
     0     1     0
     0     0     1
A
A =
      0.81472      0.91338       0.2785
      0.90579      0.63236      0.54688
      0.12699      0.09754      0.95751
eye(3)*A
ans =
      0.81472      0.91338       0.2785
      0.90579      0.63236      0.54688
      0.12699      0.09754      0.95751
A*eye(3)
ans =
      0.81472      0.91338       0.2785
      0.90579      0.63236      0.54688
      0.12699      0.09754      0.95751
eye(3)
ans =
     1     0     0
     0     1     0
     0     0     1
rand(4,3)
ans =
      0.14189      0.95949      0.93399
      0.42176      0.65574      0.67874
      0.91574     0.035712      0.75774
      0.79221      0.84913      0.74313
C = ans
C =
      0.14189      0.95949      0.93399
      0.42176      0.65574      0.67874
      0.91574     0.035712      0.75774
      0.79221      0.84913      0.74313
C*eye(3)
ans =
      0.14189      0.95949      0.93399
      0.42176      0.65574      0.67874
      0.91574     0.035712      0.75774
      0.79221      0.84913      0.74313
eye(3)*C
{??? Error using ==> mtimes
Inner matrix dimensions must agree.
} 
eye(4)*C
ans =
      0.14189      0.95949      0.93399
      0.42176      0.65574      0.67874
      0.91574     0.035712      0.75774
      0.79221      0.84913      0.74313
a = [17 12 14 36]
a =
    17    12    14    36
x = [1;5;10;26]
x =
     1
     5
    10
    26
x = [1 5 10 25]'
x =
     1
     5
    10
    25

dot(a,x)
ans =
        1117
a*x
ans =
        1117
A = [17 12 14 36;42 0 6 40]
A =
    17    12    14    36
    42     0     6    40
x
x =
     1
     5
    10
    25
A*x
ans =
        1117
        1102
b = A*x
b =
        1117
        1102
1/2
ans =
          0.5
1\2
ans =
     2
X = [3 4;5 6]
X =
     3     4
     5     6
X^2
ans =
    29    36
    45    56
X^9
ans =
   163703163   203548204
   254435255   316364316
X-1
ans =
     2     3
     4     5
Y = X^(-1)
Y =
           -3            2
          2.5         -1.5
Y*X
ans =
            1 -1.7764e-015
 -1.7764e-015            1
X*Y
ans =
            1 -8.8818e-016
 -3.5527e-015            1
A = [.2 .7 .1;.5 .3 .4;.3 0 .5]
A =
          0.2          0.7          0.1
          0.5          0.3          0.4
          0.3            0          0.5
x = [111; 34; 68]
x =
   111
    34
    68
b = A*x
b =
         52.8
         92.9
         67.3
A*x
ans =
         52.8
         92.9
         67.3
A,b
A =
          0.2          0.7          0.1
          0.5          0.3          0.4
          0.3            0          0.5
b =
         52.8
         92.9
         67.3
x = ?
??? x = ?
         |
{Error: Expression or statement is incomplete or incorrect.
} 
x = b\A
x =
    0.0048409    0.0040652    0.0047713
x = A\b
x =
          111
           34
           68