RE: Two questions (1) Sollve and (2) Precision
- To: mathgroup at smc.vnet.net
- Subject: [mg67049] RE: [mg67035] Two questions (1) Sollve and (2) Precision
- From: "David Park" <djmp at earthlink.net>
- Date: Thu, 8 Jun 2006 04:53:16 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Use "==" for the equations, NOT "=".
djmp at earthlink.net
From: Bharat Bhole [mailto:bbhole at gmail.com]
To: mathgroup at smc.vnet.net
Would appreciate if someone can point out why Mathematica is not giving the
expected output in the followng two cases.
(1) I was trying to solve the follwing two linear equations using 'Solve'.
However, the solution exists and is given by x = 205117922, y = 83739041
Why is Mathematica unable to solve this simple linear equation? Am I doing
(2) I suppose that the default precision for numerical calculations is
MachinePrecision which is less than 16. If I increase the precision, should
I not get more accurate results? The example below seems to contradict that.
(i) Exact Calculation
*In: 123456789123 * 123456789123*
(ii) Numerical Calculation with Default Precision
*In: 123456789123 * 123456789123.0*
*Out: 1.52416 =D7 10^22*
(iii) Numerical Calcuation with a higher precision.
*In:SetPrecision[ 123456789123 * 123456789123.0 , 50 ]*
*Out: 1.5241578780560891838464000000000000000000000000000 x 10^22*
Now if I calculate Out-Out, I get zero.
But if I calculate Out-Out, I get -729335.000000000000000000000000000
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