Re: Full simplify problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg122314] Re: Full simplify problem*From*: DrMajorBob <btreat1 at austin.rr.com>*Date*: Mon, 24 Oct 2011 05:16:14 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j7u59t$u$1@smc.vnet.net> <201110231024.GAA10556@smc.vnet.net>*Reply-to*: drmajorbob at yahoo.com

Much easier is E^x - E^(y + z) /. x -> y + z 0 ...unless your real problem is more complicated? Bobby On Sun, 23 Oct 2011 05:24:44 -0500, dimitris <dimmechan at yahoo.com> wrote: > On Oct 22, 1:18 pm, "A. Lapraitis" <ffcita... at gmail.com> wrote: >> Hello, >> >> Could anyone explain why the following does not give zero? >> >> In[72]:= Assuming[ >> x == y + z, >> FullSimplify[ >> E^x - E^(y + z) >> ] >> ] >> >> Out[72]= E^x - E^(y + z) >> >> Thanks! > > Actually private communication with Andrzej Kozlowski made me > understand that the approach in my second message was incorrect. > For example each of the following evaluate to True > > In[116]:= Assuming[x === y + z, FullSimplify[E^x - E^(y + z) === > 0]] > > During evaluation of In[116]:= $Assumptions::fas: Warning: One or more > assumptions evaluated to False. >> > > Out[116]= True > > In[119]:= Assuming[x === y + z, FullSimplify[E^x - E^(y + z) < 0]] > > During evaluation of In[119]:= $Assumptions::fas: Warning: One or more > assumptions evaluated to False. >> > > Out[119]= True > > In[120]:= Assuming[x === y + z, FullSimplify[E^x - E^(y + z) > 0]] > > During evaluation of In[120]:= $Assumptions::fas: Warning: One or more > assumptions evaluated to False. >> > > Out[120]= True > > Assuming False every predicate becomes True. > > Of course the approach in the first message is correct. > > Dimitris > -- DrMajorBob at yahoo.com

**References**:**Re: Full simplify problem***From:*dimitris <dimmechan@yahoo.com>