Re: DSolve Not Working
- To: mathgroup at smc.vnet.net
- Subject: [mg44954] Re: DSolve Not Working
- From: drbob at bigfoot.com (Bobby R. Treat)
- Date: Wed, 10 Dec 2003 04:02:12 -0500 (EST)
- References: <br4254$j1n$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
EVERY DAY, we hear DSolve isn't working.
You didn't get that output from that input.
DSolve[y''[x]==ay'[x]+y[x],y,x]
{{y -> Function[{x},
E^x*C[1] + C[2]/E^x +
(E^(2*x)*Integrate[
((1/2)*Derivative[
1][ay][K$1927])/
E^K$1927, {K$1927,
K$1928, x}] +
Integrate[(-(1/2))*
E^K$2236*
Derivative[1][ay][
K$2236], {K$2236,
K$2237, x}])/E^x]}}
You omitted a space between a and y on the right side of the equation,
leading to this strange result.
The input you actually used was probably
DSolve[y''[x] == a y/x + y[x], y, x]
which returns the output in your post. On the other hard, copying and
pasting from Help gives:
DSolve[y''[x] == a y'[x] + y[x], y, x]
{{y -> Function[{x},
E^((1/2)*(a - Sqrt[
4 + a^2])*x)*C[1] +
E^((1/2)*(a + Sqrt[
4 + a^2])*x)*C[2]]}}
Bobby
Will Oram <spamguy at NOSPAM.foxchange.NOSPAM.com> wrote in message news:<br4254$j1n$1 at smc.vnet.net>...
> I'm using Mathematica 5; DSolve[] never works. I am literally copying from
> its own documentation, and it still spits out failures. For example:
>
> In: DSolve[y''[x]==ay'[x]+y[x],y,x]
> DSolve::dvnoarg: The function y appears with no arguments
> Out: DSolve[y''[x]==(ay)/x+y[x],y,x]
>
> Wha?