# Find an inverse matrix, regarding a parameter as real

I have the matrix

{{3, 2, 1}, {3, 1, 2}, {2, 3, -1},
{-(3/b), -(3/b^2) - 2/b, -(3/b^3) - 2/b^2 - 1/b},
{-(3/b), -(3/b^2) - 1/b, -(3/b^3) - 1/b^2 - 2/b},
{-(2/b), -(2/b^2) - 3/b, -(2/b^3) - 3/b^2 + 1/b}}


and I want to compute its inverse (or pseudoinverse).

The problem is that Mathematica solves this regarding b as a complex number. How do I change this to set b as real? I tried Assuming but that didn't work. Maybe I am writing it wrong. Any ideas? It should be fairly simple, but I am not really good at Mathematica and I couldn't find a solution elsewhere. I would be greatful for a general answer, not one specifically for this example; e.g., Pseudoinverse[a] /. Reals[b] -> ... (this didn't work).

Thanks

• Try ComplexExpand[PseudoInverse[mat]]. – b.gates.you.know.what Nov 17 '12 at 15:16

m={{3, 2, 1},