Re: Thread function now working as expected

*To*: mathgroup at smc.vnet.net*Subject*: [mg74612] Re: [mg74587] Thread function now working as expected*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Wed, 28 Mar 2007 01:43:26 -0500 (EST)*Reply-to*: hanlonr at cox.net

eqn1 = Sqrt[1+196*x^4] == 12*x-1-14*x^2; To square both sides of an equation just use Map (/@) eqn2 = #^2& /@ eqn1 196*x^4 + 1 == (-14*x^2 + 12*x - 1)^2 To expand both sides of an equation use ExpandAll eqn3 = eqn2//ExpandAll 196*x^4 + 1 == 196*x^4 - 336*x^3 + 172*x^2 - 24*x + 1 eqn3//Simplify x*(84*x^2 - 43*x + 6) == 0 However, you do not need to expand eqn2 to get this result eqn2//Simplify x*(84*x^2 - 43*x + 6) == 0 Bob Hanlon ---- siewsk at bp.com wrote: > I cannot get the Thread function to work on In[3] and I > am forced to do it manually in In[4] > > Does anyone has any idea why In[3] is not working as I expected? > > In[1]:= eqn1 = Sqrt[1 + 196*x^4] == 12*x - 1 - 14*x^2 > Out[1]= > 4 2 > Sqrt[1 + 196 x ] == -1 + 12 x - 14 x > > > In[2]:= eqn2 = Thread[(#1^2 & )[eqn1], Equal] > Out[2]= > 4 2 2 > 1 + 196 x == (-1 + 12 x - 14 x ) > > > In[3]:= dummy = Thread[Expand[eqn2], Equal] > Out[3]= > 4 2 2 > 1 + 196 x == (-1 + 12 x - 14 x ) > > > In[4]:= eqn3 = Equal[ eqn2[[1]] , Expand[ eqn2[[2]] ] ] > Out[4]= > 4 2 3 4 > 1 + 196 x == 1 - 24 x + 172 x - 336 x + 196 x > > > In[5]:= Simplify[eqn3] > Out[5]= > 2 > x (6 - 43 x + 84 x ) == 0 > >