*To*: mathgroup@smc.vnet.net*From*: Andrzej Kozlowski <andrzej@tuins.ac.jp>*Date*: Fri, 30 Jan 1998 04:24:12 -0500

In article <6ahorb$pkh@smc.vnet.net>, seanross@worldnet.att.net wrote: > alok. menghrajani wrote: > > > > Hi, > > > > I'm 16 and I can't understand how I (why me?) found this bug in > > mathematica. It's such a silly thing: > > > > Solve [x/x+x=1, x] returns x=0 but if x=0 then x/x has no sence! > > > > Bye, ALok > > > > (Pls reply to my email: robot@writeme.com) > > > Its not a bug. You are missing a pre-calculus course in limits. Perhaps > your high school offers one. It may sound very pedantic but I must say I feel this reply is a little unfair to Alok. The equation x/x+x== 1 is an algebraic equation and the solution {x->0} is certainly incorrect. I would fail any of my students who claimed it was, so I do not think his pointing this out is a sign of ignorance of mathematics. (To make it quite clear you can replace Alok's equation by Solve[{x/x+x==1,Modulus==5},x,Mode->Modular]. You still get the same answer though it now makes no sense to talk about limits). The reason why this is not a bug seems to me, basically, to be the fact that we expect of computers other things than of algebra students. In particular, in computer algebra strict mathematical correctness often takes second place to considerations such as speed, efficiency etc. I think one has to remember that when claiming that behaviour which does not correspond to standard mathematical practice constitutes a bug (I have found several such examples in the past archives of mathgroup). A. Kozlowski