A =

     4     2     5
     5     3     7
     1     9     2

>> Q=adjoint(A)

Q =

   -57    41    -1
    -3     3    -3
    42   -34     2

>> R=det(A)

R =

   -24

>> X=Q/R

X =

    2.3750   -1.7083    0.0417
    0.1250   -0.1250    0.1250
   -1.7500    1.4167   -0.0833

>> Y=inv(A)

Y =

    2.3750   -1.7083    0.0417
    0.1250   -0.1250    0.1250
   -1.7500    1.4167   -0.0833

Since X = Y it follows that inv(A) = adj(A)/det(A).