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Re: differential equation solve
*To*: mathgroup at smc.vnet.net
*Subject*: [mg68847] Re: [mg68821] differential equation solve
*From*: Bob Hanlon <hanlonr at cox.net>
*Date*: Mon, 21 Aug 2006 03:27:46 -0400 (EDT)
*Reply-to*: hanlonr at cox.net
*Sender*: owner-wri-mathgroup at wolfram.com
Make sure that all of your variables are clear
$Version
5.2 for Mac OS X (June 20, 2005)
Clear[x,y,t];
DSolve[{y'[x] == r*y[x], y[0] == a}, y, x]
{{y -> Function[{x}, a*E^(r*x)]}}
DSolve[{y'[x] == r*y[x], y[0] == a}, y[x], x]
{{y[x] -> a*E^(r*x)}}
Off[Solve::ifun];
DSolve[{x'[t] == r*x[t]*(1 - x[t]/xm), x[0] == x0}, x, t]
{{x -> Function[{t}, (E^(r*t)*x0*xm)/(E^(r*t)*x0 - x0 + xm)]}}
DSolve[{x'[t] == r*x[t]*(1 - x[t]/xm), x[0] == x0}, x[t], t]
{{x[t] -> (E^(r*t)*x0*xm)/(E^(r*t)*x0 - x0 + xm)}}
Bob Hanlon
---- elvis <rapstone at gmail.com> wrote:
> Here we often use mathematica to solve differential equations, when I
> encouter a equation with several constrains I set them to those values.
> But it cannot solve it and have the following warnings:
>
> DSolve::deqx: Supplied equations are not differential equations of
> the given functions.
>
> Give a very simple differential equation here:
>
> DSolve[{y'[x] == r*y[x], y[0] == a}, y, x]
>
> another equation:
>
> \!\(DSolve[{\(x'\)[t] == r*x[t] \((1 - x[t]\/xm)\), x[0] == x0}, x,
> t]\)
>
> this face anothe prolbem
>
> Can anyone help to "solve" this problem for me?
> Thanks!
>
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