Re: Re: Non-algebraic solution

*To*: mathgroup at smc.vnet.net*Subject*: [mg52458] Re: [mg52421] Re: [mg52399] Non-algebraic solution*From*: DrBob <drbob at bigfoot.com>*Date*: Sun, 28 Nov 2004 01:06:38 -0500 (EST)*References*: <Pine.LNX.4.44.0411271159360.16427-100000@crest.ernet.in>*Reply-to*: drbob at bigfoot.com*Sender*: owner-wri-mathgroup at wolfram.com

In that case, symbolic solutions are probably impossible. But numerical solutions are still doable: Clear[ySolve] ySolve[a_, b_, c_, d_][(x_)?NumericQ] := E^logY /. First[FindRoot[ Log[E^logY/a] + b*Log[c + E^logY/d] == -x, {logY, 50.}]] plot = Plot[ySolve[3.1, 2.5, 1.07, 4.3][x], {x, -25, 5}]; Bobby On Sat, 27 Nov 2004 12:01:35 +0530 (IST), B.Ravinder <ravi at crest.ernet.in> wrote: > But the problem in my case is that a, b, c, d are Non-integer number. > > > > On Fri, 26 Nov 2004, DrBob wrote: > >> It can be solved and plotted for some values of the parameters. >> >> For instance: >> >> Clear[x, y] >> Block[{a = 3, >> b = 2, c = 1, d = 4, equation = Log[y/a] + b*Log[c + y/d] == -x}, >> Solve[equation, y] >> ]; >> y[x_] = y /. First@% >> Plot[y@x, {x, -25, 10}] >> >> Bobby >> >> On Fri, 26 Nov 2004 01:04:27 -0500 (EST), B.Ravinder <ravi at crest.ernet.in> wrote: >> >> > Dear all, >> > I want to plot the following type of logarithmic equation having >> > dependent variable y and independent variable x. >> > >> > Log[y/a] + b*Log[c+y/d] = -x >> > >> > where a,b,c and d are some arbitrary constants. >> > >> > First I tried to solve the equation for y using Solve function in >> > Mathematica 4.2, but got the following error >> > message: >> > Solve:: tdep : >> > The equations appear to involve the variables to be solved >> > for in an essentially non-algebraic way. >> > >> > >> > Could someone please guide me as to how do we solve such equation >> > with/without Mathematica. >> > or >> > If possible, how to obtain y vs. x plot in Mathematica without soving them >> > exactly. >> > Waiting for the kind resonse. >> > >> > Regards, >> > Ravi >> > >> > >> > >> > >> >> >> >> > > > > -- DrBob at bigfoot.com www.eclecticdreams.net