Replacement gyrations

*To*: mathgroup at smc.vnet.net*Subject*: [mg55872] Replacement gyrations*From*: carlos at colorado.edu*Date*: Fri, 8 Apr 2005 01:37:00 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

A Solve for 4 variables W11,W12,W21,W22 produces, after Simplify Wsol={{W11 -> (A2*x21 + A1*x32)/(L86^2*(-(x32*y21) + x21*y32)), W12 -> (A2*y21 + A1*y32)/(-(L86^2*x32*y21) + L86^2*x21*y32), W21 -> (A2*x21 + A1*x32)/(L75^2*(-(x32*y21) + x21*y32)), W22 -> (A2*y21 + A1*y32)/(-(L75^2*x32*y21) + L75^2*x21*y32)}} Question 1: why do L86^2 and L75^2 come out as a factor in two expression denominators and not in the others? Seems a random event. This uncertainty inhibits the action of further replacement rules such as (-(x32*y21) + x21*y32) -> 2*A123 which works on W11 and W21 only. Question 2: I tried Collect [Wsol,{L86,L75}] to try to force grouping of L86^2 and L75^2, but it has no effect. Do I need to say Wsol=Wsol*L86^2*L75^2, Simplify, replace and finally Wsol=Wsol/L86^2*L75^2 ? Or fool around with Numerator and Denominator?

**Follow-Ups**:**Re: Replacement gyrations***From:*Daniel Lichtblau <danl@wolfram.com>

**Re: Replacement gyrations***From:*DrBob <drbob@bigfoot.com>