Re: Differencing two equations
- To: mathgroup at smc.vnet.net
- Subject: [mg129765] Re: Differencing two equations
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Mon, 11 Feb 2013 04:39:13 -0500 (EST)
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On 2/10/13 at 3:24 AM, g.c.b.at.home at gmail.com wrote: >I'm trying to figure out how to difference two equations. Basically >if I have: a==r >b==s >I'd like to get: a-b == r-s >What I'm getting is more like (a==r) - (b==s). I'm not sure how >that's a useful result, but is there a function to do what I'm >looking for? >A quick search of the archives seem to bring up ways of doing this >from using transformation rules to swap heads to unlocking the >Equals operator and hacking its behavior. I'd like to avoid doing >that kind of rewiring for a simple operation, and I'd like to keep >the syntax clean. Here is one way, but it may not meet your criteria for clean syntax In[1]:= eq1 = a == r; eq2 = b == s; In[3]:= Equal @@ (Subtract @@ List @@@ {eq1, eq2}) Out[3]= a-b==r-s