Re: Extracting terms from an equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg69826] Re: Extracting terms from an equation*From*: albert <awnl at arcor.de>*Date*: Sat, 23 Sep 2006 23:45:40 -0400 (EDT)*References*: <eevubf$hqu$1@smc.vnet.net> <ef2t04$mjc$1@smc.vnet.net>

Hi, > Cases[a + b*x^2 + c*y^2 + d*x*y + e*x^3, _?( !FreeQ[#1, x] & )] > {b*x^2, e*x^3, d*x*y} > > Cases[a + b*x^2 + c*y^2 + d*x*y + e*x^3, _?(MemberQ[#1, x] & )] > {d*x*y} MemberQ by default checks for precense of x in the first level only. What you probably want is: Cases[a + b*x^2 + c*y^2 + d*x*y + e*x^3, _?(MemberQ[#1, x,Infinity] & )] which should always give the same result as the version with FreeQ. Use In[4]:= FullForm[e*x^3] Out[4]//FullForm= Times[e, Power[x, 3]] to understand why x is not a member of e*x^3 , but x^3 is... hth, albert