       Re: problem in expression

• To: mathgroup at smc.vnet.net
• Subject: [mg99918] Re: [mg99889] problem in expression
• From: "David Park" <djmpark at comcast.net>
• Date: Tue, 19 May 2009 06:45:49 -0400 (EDT)
• References: <12990926.1242642314726.JavaMail.root@n11>

```Numbers with decimal points are approximate numbers rather than exact
numbers. As soon as you introduce a decimal point into a calculation it will
be done entirely with approximate numbers. This might often be the normal
manner of doing it. Mathematica is saying it doesn't know if those terms are
exactly zero.

In some cases you may be able to formulate your equations entirely with
exact numbers (integers, rational numbers, exact roots) and then you will
obtain exact answers - if Mathematica can solve it.

Otherwise you can use Chop on your output to get rid of the 0. terms and
Rationalize to get rid of the 1. Factor.

David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/

From: Obaid Ur Rehman [mailto:Obaid.Rehman at student.adfa.edu.au]

I am wondering if some one can help me in the following problem.

Whenever I solve or do some manipulation with certain matrix or vector,
it gives me result in the following form e.g.

F=0.x1+0.x2+1.x3+0.x4

It is clear that F=x3 but why the expression contains multiples of
zeros. If certain vector is multiplied by zero the result should be zero
and it must not be appear in the final expression.

final expression?

Obaid

```

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