Matrix Inverse Issue

*To*: mathgroup at smc.vnet.net*Subject*: [mg80556] Matrix Inverse Issue*From*: "Brian Gladman" <brg at nowhere.org>*Date*: Sun, 26 Aug 2007 03:00:40 -0400 (EDT)

I am having a problem with the matrix inverse for the following matrix in Mathematica 6: A = Table[If[j == i, 1 - i/10, If[j == i + 1, i/10, 0]], {i, 9}, {j, 9}] {{9/10, 1/10, 0, 0, 0, 0, 0, 0, 0}, {0, 4/5, 1/5, 0, 0, 0, 0, 0, 0}, {0, 0, 7/10, 3/10, 0, 0, 0, 0, 0}, {0, 0, 0, 3/5, 2/5, 0, 0, 0, 0}, {0, 0, 0, 0, 1/2, 1/2, 0, 0, 0}, {0, 0, 0, 0, 0, 2/5, 3/5, 0, 0}, {0, 0, 0, 0, 0, 0, 3/10, 7/10, 0}, {0, 0, 0, 0, 0, 0, 0, 1/5, 4/ 5}, {0, 0, 0, 0, 0, 0, 0, 0, 1/10}} A Inverse[A] {{1, -1/72, 0, 0, 0, 0, 0, 0, 0}, {0, 1, -1/14, 0, 0, 0, 0, 0, 0}, {0, 0, 1, -3/14, 0, 0, 0, 0, 0}, {0, 0, 0, 1, -8/15, 0, 0, 0, 0}, {0, 0, 0, 0, 1, -5/4, 0, 0, 0}, {0, 0, 0, 0, 0, 1, -3, 0, 0}, {0, 0, 0, 0, 0, 0, 1, -49/6, 0}, {0, 0, 0, 0, 0, 0, 0, 1, -32}, {0, 0, 0, 0, 0, 0, 0, 0, 1}} I expected the identity matrix here but I get extra terms. Am I doing something wrong? Brian Gladman

**Follow-Ups**:**Re: Matrix Inverse Issue***From:*Murray Eisenberg <murray@math.umass.edu>

**Re: Matrix Inverse Issue***From:*Sseziwa Mukasa <mukasa@jeol.com>