M=
  -0.5502    0.5154    0.4739 
    1.368   -0.9168   -0.1241 
   -2.011   -0.4928    0.3926 
qrm.A=
    2.494   -0.2194   -0.4892 
    1.953     1.141   0.05019 
   -0.938     -1.69   -0.3901 
b=
  -0.9292   0.07983   -0.1595 
x=
   -0.268   -0.2104    -2.043 
A*x=
  -0.9292   0.07983   -0.1595 
M*x-b
1.849e-16 4.555e-17 -8.674e-17 
MI=
   0.3795    0.3928   -0.3338 
   0.2591    -0.664   -0.5228 
    2.269     1.178     0.181 
MI*M=
        1 3.334e-18 2.575e-18 
-1.677e-16         1 2.631e-17 
-2.73e-16 -2.078e-17         1 
M*MI=
        1 -6.614e-18 1.235e-16 
6.329e-17         1 -1.464e-16 
-3.15e-17 -7.186e-17         1