Re: How to plot this

*To*: mathgroup at smc.vnet.net*Subject*: [mg64454] Re: How to plot this*From*: Jon Harrop <usenet at jdh30.plus.com>*Date*: Fri, 17 Feb 2006 04:12:35 -0500 (EST)*References*: <dt1coe$5j$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

siegmund natter wrote: > Can anyone tell why this is wrong? > > eqn1 = x + y == 2*x*y; > eqn1 /.y -> y[x]; > Plot[y[x], {x, 1, 3}] > > How do I do it correctly? (This is just an example; I want to do this > with a much more difficult equation) > Thanks a lot. You can solve for y to get an expression for y[x]: In[1]:= eqn1 = x + y == 2*x*y; In[2]:= y[x_] = First[y /. Solve[eqn1, {y}]] x Out[2]= -------- -1 + 2 x which you can then plot: In[3]:= Plot[y[x], {x, 1, 3}]; You could also use something like InequalityPlot to highlight the same border: In[4]:= << Graphics`InequalityGraphics` In[5]:= InequalityPlot[x + y < 2*x*y , {x, -3, 3}, {y, -3, 3}]; -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. http://www.ffconsultancy.com/products/ocaml_for_scientists/chapter1.html