Re: very odd failure of Solve

*To*: mathgroup at smc.vnet.net*Subject*: [mg131654] Re: very odd failure of Solve*From*: Richard Fateman <fateman at cs.berkeley.edu>*Date*: Mon, 16 Sep 2013 05:15:47 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <l1446c$psj$1@smc.vnet.net>

On 9/15/2013 4:03 AM, Alan wrote: > Setting an irrelevant parameter to 0 baffles Solve. Why? > Thanks, > Alan Isaac > > $Assumptions =. > ClearAll[f1] > f1[x_] := s*x^\[Alpha] - (a + b + c)*x > Solve[f1[x] == 0, x] (* Solve works *) > Solve[(f1[x] /. {b -> 0}) == 0, x] (* Solve fails *) <snip> Running Reduce[ {%==0}, {x} ] on either equation seems to go into an infinite loop. That maybe be an independent bug, though. I expected that somehow fiddling with the variable names would do something, and that the ordering of a,b,c, alpha was critical. Out of curiosity I tried a few variants to generate a better hypothesis, but ran out of, um, curiosity.