Re: Question about how to graph the vector field for the differential

*To*: mathgroup at smc.vnet.net*Subject*: [mg97856] Re: Question about how to graph the vector field for the differential*From*: Erik Max Francis <max at alcyone.com>*Date*: Tue, 24 Mar 2009 05:29:18 -0500 (EST)*References*: <gq7j9f$qeo$1@smc.vnet.net>

jo1e984 at gmail.com wrote: > i need to graph the vector field and the family of solutions for the > DE: dy/dx=2x-y > and i tried the graph the vector field, but while i tried to use the > VectorFieldPlot it show up some kind of wierd graph... > and i cannot even get start on the "family of Solutions" > graph...searched online but still cannot figure out. > hope some pros can help me out on this...thx alot~!! It's not clear what you're trying to accomplish. Your differential equation involves one function, y(x), and one independent variable, x. This isn't a vector at all. Written into Mathematica-speak: In[1]:= sol = DSolve[y'[x] == 2 x - y[x], y[x], x] Out[1]= {{y[x] -> 2 (-1 + x) + E^-x C[1]}} If you want to plot this, pull out the solution and play with it (%1 /. sol[[1]]). If you want to graph it, just use Plot, but you'll have to specify a value of the constant of integration C[1]. -- Erik Max Francis && max at alcyone.com && http://www.alcyone.com/max/ San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M erikmaxfrancis The only completely consistent people are the dead. -- Aldous Huxley