Re: finding inverses of functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg126426] Re: finding inverses of functions*From*: Peter Breitfeld <phbrf at t-online.de>*Date*: Thu, 10 May 2012 04:55:41 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <jod7lu$5f8$1@smc.vnet.net>

John Accardi wrote: > Hello, I am trying to get Mathematica to find the inverse of: > > y = 3x^3 + 2e^(2x) (which I know is invertible) > > InverseFunction only seems to give inverses of built-ins, like Sine. > > I tried: > > Solve[ y == 3x^3 + 2e^(2x), x ] but get a message that Solve does not have methods suitable. (Solve works for simpler functions, however.) > > Any ideas? Thanks. > Because your function is trancendental you can't hope for a closed form. But InverseFunction can be used: f[x_] = 3 x^3 + E^(2 x) g[y_] = InverseFunction[f][y] Plot[f[x], {x, -2, 3}] Plot[g[y], {y, -50, 250}] -- _________________________________________________________________ Peter Breitfeld | Bad Saulgau, Germany | http://www.pBreitfeld.de