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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg97862] Re: Question about how to graph the vector field for the differential
  • From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
  • Date: Tue, 24 Mar 2009 05:30:28 -0500 (EST)
  • References: <gq7j9f$qeo$1@smc.vnet.net>

I have the feeling you're looking for the wrong type of plot. Your
differential equation yields a family of funtions of x and these can
be plotted simply by using Plot.

First, solve the differntial equation:

In[20]:= DSolve[y'[x] == 2 x - y[x], y[x], x]

Out[20]= {{y[x] -> 2 (-1 + x) + E^-x C[1]}}

Then plot it for some values of the constant C[1]:

Plot[Table[2 (-1 + x) + E^-x c, {c, -10, 10, 5}] // Evaluate, {x, -1,
  5}, PlotRange -> All]

Cheers -- Sjoerd

On Mar 23, 11:03 am, jo1e... 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~!!
> Bluefly



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