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Re: Inverse function warnings

  • To: mathgroup at smc.vnet.net
  • Subject: [mg99238] Re: Inverse function warnings
  • From: dh <dh at metrohm.com>
  • Date: Thu, 30 Apr 2009 06:25:34 -0400 (EDT)
  • References: <gt90og$l55$1@smc.vnet.net>


Hi,

your equation is a transcendental equation with infinitely many 

solutions. Reduce gets them all. You get them by setting C[1] to some 

arbitrary integer.

You may eliminate the warning by:

Quiet@Solve[3^(2 x) - 12 (3^x) + 27 == 0, x]

Daniel



davef wrote:

> When I execute this in Mathematica 7:

> 

> Solve[3^(2 x) - 12 (3^x) + 27 == 0, x]

> 

> I get this:

> 

> Solve::ifun: Inverse functions are being used by Solve, so some solutions may not be found; use Reduce for complete solution information. >> 

> 

> {{x->1},{x->2}}

> 

> 

> 1 amd 2 are proper solutions but is it possible to avoid the warning?

> 

> If I use Reduce:

> 

> Reduce[3^(2 x) - 12 (3^x) + 27 == 0, x]

> 

> I get a set of 1 and 2 added to some imaginary number terms that I don't quite understand.

> 

> I guess my question is: why would the use of inverse functions be so unreliable a solution as to necessitate a warning?  And in the interest of clean output, can the warning be supressed other than by deleteing the cell?  

> 

> Thanks

> 




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