(*						      *)
(* Numerical Mathematics and Computing, Fifth Edition *)
(* Ward Cheney & David Kincaid		              *)
(* Brooks/Cole Publ. Co.			      *)
(* (c) 2004                                           *)
(* No warranties implied or expressed.	              *)
(* File: p_inv1 				      *)

(* evaluating a minimal solution by finding the pseudoinverse of a matrix *)
m = Table[Random[],{20},{3}]
b = Table[Random[],{20}]
p = PseudoInverse[m]
xmin = p.b
r = m.xmin - b
Transpose[m].r