Re: Different (real) solutions using Solve for same equation
- To: mathgroup at smc.vnet.net
- Subject: [mg101847] Re: [mg101807] Different (real) solutions using Solve for same equation
- From: Murray Eisenberg <murray at math.umass.edu>
- Date: Sun, 19 Jul 2009 07:15:10 -0400 (EDT)
- Organization: Mathematics & Statistics, Univ. of Mass./Amherst
- References: <200907180848.EAA06417@smc.vnet.net>
- Reply-to: murray at math.umass.edu
You have a typo in your second Solve, below. Once you fix that, you should obtain the same solutions: old = Solve[w/p == 25 e^2/(e + w)^2, w]; new = Solve[w^3 + 2 e w^2 + w e^2 == 25 p e^2, w]; old == new True kristoph wrote: > Dear all, > > I came across the following observation which I find troublesome. > > I was trying to solve the equation w/p == 25 e^2 / (e + w)^2 using > Solve[w/p == 25 e^2 / (e + w)^2 , w]. But the non-complex solution did > not have the properties I wanted. > > I tested whether the solution was right and tried solving w^3 + 2 e > w^2 w e^2 == 25 p e^2 (which is just rewriting the first equation) > using Solve[w^3 + 2 e w^2 w e^2 == 25 p e^2, w]. > > This time the properties were present and the two non-complex > solutions using the first and second approach where different. I would > like to know why? Each equation can be transformed into the other via > simple operations, why are there different solutions to it? > > Thanks for answer. > -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305
- References:
- Different (real) solutions using Solve for same equation ?
- From: kristoph <kristophs.post@web.de>
- Different (real) solutions using Solve for same equation ?