Re: Equations system with zero

*To*: mathgroup at smc.vnet.net*Subject*: [mg91374] Re: [mg91360] Equations system with zero*From*: DrMajorBob <drmajorbob at att.net>*Date*: Tue, 19 Aug 2008 07:13:55 -0400 (EDT)*References*: <27595538.1219046810354.JavaMail.root@m08>*Reply-to*: drmajorbob at longhorns.com

y/(9y) is undefined (meaningless) when y is zero. End of story. Bobby On Mon, 18 Aug 2008 02:36:41 -0500, Miguel <mibelair at hotmail.com> wrote: > Hi alll, > > Let the following equations system for x, y Reals > > Solve[{y/(9y)==0/(5x),x^2+3y^2},{x,y}] > {} > > Mathematica 6.0.1 yields no solution. But the solutions exist. They > are four solutions > > x=0, y=+-Sqrt[1/3] > y=0, x=+-1 > > Mathematica first simplifying y/(9y) -> 1/9 and it compare with 0/(5x) - >> and yiels False and it stops the process. Is this correct?. > > In my opinion, the correct process would be > (5*x*y)==(9*y*0) > 5xy=0 ----> x=0 or y=0 > > and substitution in the second equation. > > -- DrMajorBob at longhorns.com