seruous solve bug? only when used with simplifying

*To*: mathgroup at smc.vnet.net*Subject*: [mg48634] seruous solve bug? only when used with simplifying*From*: sean_incali at yahoo.com (sean kim)*Date*: Wed, 9 Jun 2004 04:16:50 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

hello group, i think i have a serious Solve[], Simplify[], FullSimplify[] bug... Take a system of equations as below. (apb is actually (a+b). i defined it as apb to keep Mathematica crunching away at it) sys = {c1[t] == (c*(16*a^4 + 8*a^3*kd + 4*a^2*apb*kd + 2*a*apb^2*kd + apb^3*kd))/(apb^4*kd), c2[t] == (2*(8*a^3 + 4*a^2*apb + 2*a*apb^2 + apb^3)*b*c)/(apb^4*d), c3[t] == (2*(8*a^3 + 4*a^2*apb + 2*a*apb^2 + apb^3)*b*c)/(apb^4*kd)} sys1 = sys /.{apb -> (a + b)} sys2 = sys/.{apb -> (a + b)}//Simplify sys3 = sys/.{apb -> (a + b)}//FullSimplify and then use TrueQ[sys1 == sys1] TrueQ[sys1 == sys2] TrueQ[sys1 == sys3] TrueQ[sys2 == sys3] then it gives, Out[18]=True Out[19]=False Out[20]=False Out[21]=False Simplify and FullSimplify changed the system so much that they are not equal? Basically, unless I define the (a+b) as a single constant apb, the Mathematica will do soemthing with it then it messes it up. I think... Why is this happening? and how do i prevent it from happening again with other more obsucre systems? Above I got lucky in finding the cause (a+b) thanks in advance for any and all comments. Sean

**Follow-Ups**:**Re: seruous solve bug? only when used with simplifying***From:*Andrzej Kozlowski <akoz@mimuw.edu.pl>

**Re: seruous solve bug? only when used with simplifying***From:*DrBob <drbob@bigfoot.com>