Re: Plot results not right

*To*: mathgroup at smc.vnet.net*Subject*: [mg89889] Re: Plot results not right*From*: "David W.Cantrell" <DWCantrell at sigmaxi.net>*Date*: Tue, 24 Jun 2008 03:25:25 -0400 (EDT)*References*: <g3nhbc$g6$1@smc.vnet.net>

BrenB <GoogleGroups at ebesser.com> wrote: > I'm new to Mathematica. > > I'm studying Calculus, and I'm trying to reproduce, in Mathematica, > the graph results of an equation in my book. > > Plot[2 x - 3 x^(2/3) + 4, {x, -1, 6}] > > The output graph is correct, except there should be graphing in the > 2nd and 3rd quadrant, and there is none. > > Is there another way to enter this equation into Mathematica to get > the correct graph results? Yes: Plot[2 x - 3 (x^2)^(1/3) + 4, {x, -1, 6}] Note that, for negative x, x^(2/3) and (x^2)^(1/3) are not the same in Mathematica. The latter expression gives a positive value, which is what you want, while the former expression gives the _principal_ value of the 2/3 power, which has a nonzero imaginary part and so does not plot. David