--- a/share/linearalgebra/matrixexp.lisp
+++ b/share/linearalgebra/matrixexp.lisp
@@ -138,8 +138,8 @@
(print `(ratvars = ,$ratvars gcd = '$gcd algebraic = ,$algebraic))
(print `(ratfac = ,$ratfac))
(merror "Unable to find the spectrum")))
-
- (setq res ($fullratsimp (ncpower (sub (mult z ($ident n)) mat) -1) z))
+
+ (setq res ($fullratsimp ($invert_by_lu (sub (mult z ($ident n)) mat) '$crering) z))
(setq m (length sp))
(dotimes (i m)
(setq zi (nth i sp))