Re: Forcing mathematica to output a certain form
- To: mathgroup at smc.vnet.net
- Subject: [mg108140] Re: Forcing mathematica to output a certain form
- From: Geico Caveman <spammers-go-here at spam.invalid>
- Date: Tue, 9 Mar 2010 06:21:57 -0500 (EST)
- References: <hn2mkv$4bc$1@smc.vnet.net>
On 2010-03-08 04:22:07 -0700, Bob Hanlon <hanlonr at cox.net> said: > > expr = f[t] + g[t] y'[t] == h[t] y[t]^2; > > Reverse[Expand[ > Equal @@ > Solve[expr /. > f[t] -> -z*g[t], z][[1, 1]]] /. > > z -> -f[t]/g[t]] > > Derivative[1][y][t] - (h[t]*y[t]^2)/g[t] == -(f[t]/g[t]) > > Expand[ > (First[expr] - Last[expr])/g[t]] == 0 > > f[t]/g[t] - (h[t]*y[t]^2)/g[t] + Derivative[1][y][t] == 0 > > > Bob Hanlon > > ---- Geico Caveman <spammers-go-here at spam.invalid> wrote: > > ============= > As a result of an Eliminate function, and subsequent (wrapper) > simplification under some conditions, I am getting a non-linear > differential equation. > > It looks like: > > f(t)+g(t) y'(t)=h(t) y^2(t) > > Is there a way to force mathematica to output this in the way a > differential equation is best written: > > y'(t)+h(t)/g(t) y^(t) = -f(t)/g(t) > > or > > the transposed form with zero on RHS ? Thanks for your response (and the other person's response). So, I take it that there is no way to tell Mathematica to output it in a standard form for differential equations, short of "doing it by hand" ?