RE: Eliminating (-1)^2
- To: mathgroup at smc.vnet.net
- Subject: [mg16535] RE: [mg16402] Eliminating (-1)^2
- From: "Ersek, Ted R" <ErsekTR at navair.navy.mil>
- Date: Tue, 16 Mar 1999 04:00:13 -0500
- Sender: owner-wri-mathgroup at wolfram.com
I have a slight improvement to the earlier solution I had to a question Nicolas B.E. Sawyer sent in. The question was: ------------------------ 1) How do I get Mathematica to eliminate factors of (-1)^2. Specifically I want to replace occurrences of (-(1-a)x -a y)^2 by ((1-a)x +a y)^2 within an expression? ------------------------ The replacement rule below will do what you want. I made it a little more general. The version below will work for any even exponent. In[23]:= FactorRule= expr:(_+__)^n_?EvenQ:> (Map[-#&,Part[expr,1],1]^n/. Times[-1,a_,b___]:>-a*b); In[24]:= (-(1 -a)x - a y)^2 /.FactorRule Out[24]= ((1 - a)*x + a*y)^2 ----------------------------- My previous version ended with the rule Times[-1,a_Plus,b___]:>-a*b); The version above should work better. Regards, Ted Ersek