Re: HELP! algebraic math problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg2950] Re: HELP! algebraic math problem*From*: bshoels at rs1.tcs.tulane.edu (Brett Shoelson)*Date*: Sun, 14 Jan 1996 03:43:12 -0500*Organization*: Tulane University

DavidA.Johnson at news.acns.nwu.edu wrote: : I'm stumped! : I have a simple problem that I certainly should be able to see the solution and my memory just isn't working. Is there anyone who can help me solve this. : I have a general equation of: d = a + bx + c ln(x) : I want to isolate x, how do I do it? : In reality I know a, b, c, and d and need to calculate x : I've been trying to solve this in Mathematica and it just doesn't work because of limitations in their solve routine. Of course I've been lazy for quite a while and have been using Mma to much to solve problems and my mind has obviously forgotten simple concepts. : appologetically, and in advance, THANK'S, : David A. Johnson : please email any solution or suggestions. This works, as long as you have numerical values of a,b,c,d. (Otherwise it's a much more difficult <possible?> problem: IN: ClearAll[d,a,b,c,x] ans = Roots[d==a + b x + c Log[x]/.{a->2,b->6,c->4,d->5},x] OUT: x == (3 - 4*Log[x])/6 IN: FindRoot[ans,{x,1}] OUT: {x -> 0.7194822665641975156} Note that you can also plug this equation into an HP or TI scientific calculator (or "equivalent"--although there is no equivalent of an HP) and it will spit out an answer for x. Regards, Brett Shoelson bshoels at rs6000.tcs.tulane.edu ==== [MESSAGE SEPARATOR] ====