RE: Solve weirdness

*To*: mathgroup at smc.vnet.net*Subject*: [mg35032] RE: [mg35001] Solve weirdness*From*: "DrBob" <majort at cox-internet.com>*Date*: Thu, 20 Jun 2002 02:13:41 -0400 (EDT)*Reply-to*: <drbob at bigfoot.com>*Sender*: owner-wri-mathgroup at wolfram.com

The second ^ in that line of code looks like a typo; it caused an error message. When I eliminated that, the results were an error message and the following answer: Solve[{k*0.01^p == 10, k*0.1 == 1}, {k, p}] Solve::ifun:Inverse functions are being used by Solve, so some solutions may not be found. {{k -> 10., p -> 0.}} Your answer doesn't satisfy the first condition, even if I've misinterpreted the second: k*.01^p == 10 /. {{k -> 10., p -> -1.}} {False} If I add a p to the second condition rather than eliminating ^, the following returns unevaluated with an error message: Solve[{k*0.01^p == 10, k*0.1^p == 1}, {k, p}] Solve::tdep: The equations appear to involve the variables to be solved for in an essentially non-algebraic way. Solve[{0.01^p*k == 10, 0.1^p*k == 1}, {k, p}] However, if that second reading of the problem is correct, and if we eliminate approximations, here's a solution: Off[Solve::"ifun"] eqns = {k*(1/100)^p == 10, k*(1/10)^p == 1}; Solve[#/eqns[[2, 1]] & /@ eqns[[1]], k] Solve[eqns[[2]] /. %, p] {k, p} //. Flatten[{%, %%}] {{k -> 10^(1 + 2*p)}} {{p -> -1}} {1/10, -1} Perhaps we're using different Mathematica versions; I'm using 4.1 for Windows. Bobby Treat -----Original Message----- From: Joshua A. Solomon [mailto:J.A.Solomon at city.ac.uk] To: mathgroup at smc.vnet.net Subject: [mg35032] [mg35001] Solve weirdness shouldn't Solve[{k*.01^p==10,k*.1^==1},{k,p}] produce {{k->10.,p->-1.}} ? it doesn't. it produces {{}} . what's up with that? js -- Joshua A. Solomon Department of Optometry and Visual Science City University London EC1V 0HB Voice: (44) 20 7040 0192 Fax: (44) 20 7040 0182 J.A.Solomon at city.ac.uk http://www.staff.city.ac.uk/~solomon