Re: Matrices with Mathematica 5.1

*To*: mathgroup at smc.vnet.net*Subject*: [mg63331] Re: Matrices with Mathematica 5.1*From*: Bill Rowe <browe51 at earthlink.net>*Date*: Sat, 24 Dec 2005 07:18:56 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

On 12/23/05 at 5:08 AM, drizkol at gmail.com (drizkol) wrote: >I would like to solve the system given by: >[1 7 -2 0 -8 -3] >[0 0 1 1 6 5] >[0 0 0 1 3 9] >[0 0 0 0 0 0] >Where the matrix is a typical matrix in the form x1+x2+...+xn = b >where b is the last item in the row. For example, row 1 could be >written as x1 + 7x2 - 2x3 -8x4 = -3. How could I get mathematica >to solve this matrix? I understand how to build a matrix, I just >need to know the operation to run on it. I tried to use >LinearSolve but I did something wrong. Is there a built-in >operation to solve these matrices? If so, please tell. Thanks. LinearSolve is the built in function used to solve such a problem. The reason LinearSolve won't work in this case is because your matrix represents an undetermined system. That is taking each column (except the last) to be a variable, you have 5 unknowns and 3 conditions. The last row does nothing for you since it represents the trivial identity 0==0.