Re: smart change of variables?
- To: mathgroup at smc.vnet.net
- Subject: [mg87713] Re: smart change of variables?
- From: dh <dh at metrohm.ch>
- Date: Wed, 16 Apr 2008 05:01:07 -0400 (EDT)
- References: <fu21bk$rb6$1@smc.vnet.net>
Sorry , just made a type. Here is the correct code: Solve[{expr==(k1+2 k2) (p1+2 p2),p1+p2==k1+k2,s==(p1+p2)^2,t==(-k1+p1)^2,u==(-k2+p1)^2},expr,{p1,p2,k1,k2}] Daniel Barrow wrote: > Dear all, > > I have a arithmetic problem. > I have an expression expr = (p1 + 2*p2)*(k1 + 2*k2) > where p1 + p2 = k1 + k2 > I wanna make the following change of variables, > s = (p1 + p2)^2 > t = (p1 - k1)^2 > u = (p1 - k2)^2 > > Is it possible to tell Mathematica to express expr > in terms of s, t, and u automatically? > > Thanks so much. > any ideas would be appreciated. > Sincerely Barrow >