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Re: Difference /recurrence equations

• To: mathgroup at smc.vnet.net
• Subject: [mg35174] Re: Difference /recurrence equations
• From: Peter Pein <petsie at arcor.de>
• Date: Fri, 28 Jun 2002 02:31:05 -0400 (EDT)
• Organization: Arcor
• References: <af990o$8u$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

Andrew Biggs wrote:
> I'm new to Mathematica and am having trouble with inputting the
> equations I'm looking to solve. I know the basic input of RSolve, but
> can't quite get it. Here's a sample problem, if anyone could show me
> how to input into RSolve I can probably run with the ball after that.
> 
> y(t+2) - 2Y(t+1) + 3Y(1) = 4
> 
> With the part in brackets being a subscript denoting time. I know it
> sounds dumb, but I just don't know the input notatin well enough to
> get a problem typed in correctly, and the Mathematica book is a little
> overwhelming.
> 
> Any help greatly appreciated!
> 
> Andrew
> 

Hi Andrew,

  first load the Package:

<<DiscreteMath`RSolve`

use only upper- or only lowercase Letters for the same function,
use brackets, not braces,
use == for equations, = to assign values.

RSolve[y[t+2]-2*y[t+1]+3*y[1]==4,y[t],t]

you should learn how to use rules.

Have fun,
   Peter