M=
    0.515     -0.55      1.37 
    0.474    -0.124    -0.917 
   -0.493     -2.01    -0.929 
    0.393     -0.16    0.0798 

qrm.A=
    0.942     0.622     0.807 
    0.743         2     0.357 
   -0.613     -1.43      1.67 
     0.43    -0.232     -3.02 

b=
   -0.428    0.0222    -0.117    -0.532 
x=
    -0.44     0.222    -0.132 
M*x=
    -0.53    -0.114    -0.106    -0.219 
M*x-b
   -0.102    -0.137    0.0115     0.313 
M*x==b ? : 0
MI=
    0.442     0.934    -0.223      0.56 
   -0.292     -0.03    -0.408   -0.0931 
    0.387    -0.444   -0.0734   -0.0648 

MI*M=
        1 -2.36e-16 -2.57e-16 
-2.08e-17         1 -6.42e-17 
-1.04e-17 -3.64e-17         1 

M*MI=
    0.918    -0.109   0.00921     0.251 
   -0.109     0.853    0.0123     0.336 
  0.00921    0.0123     0.999   -0.0283 
    0.251     0.336   -0.0283     0.229 



M=
 5.154e-01 -5.502e-01  1.368e+00 
 4.739e-01 -1.241e-01 -9.168e-01 
-4.928e-01 -2.011e+00 -9.292e-01 
 3.926e-01 -1.595e-01  7.983e-02 
qrm.A=
 9.419e-01  6.221e-01  8.070e-01 
 7.434e-01  2.000e+00  3.573e-01 
-6.133e-01 -1.426e+00  1.675e+00 
 4.299e-01 -2.324e-01 -3.019e+00 
b=
-4.278e-01  2.222e-02 -1.175e-01 -5.318e-01 
x=
-4.396e-01  2.216e-01 -1.324e-01 
M*x=
-5.298e-01 -1.144e-01 -1.060e-01 -2.185e-01 
M*x-b
-1.020e-01 -1.366e-01  1.150e-02  3.133e-01 
M*x==b ? : 0
MI=
 4.419e-01  9.342e-01 -2.230e-01 
-2.918e-01 -2.996e-02 -4.082e-01 
 3.873e-01 -4.439e-01 -7.342e-02 
MI*M=
 7.803e-01  8.925e-02 -4.467e-02 
 3.655e-02  9.851e-01  7.433e-03 
 2.544e-02 -1.034e-02  1.005e+00 
M*MI=
 9.183e-01 -1.094e-01  9.208e-03 
-1.094e-01  8.534e-01  1.233e-02 
 9.208e-03  1.233e-02  9.990e-01 
 2.509e-01  3.361e-01 -2.828e-02