Re: Why isn't Expand[] grouping terms by order?

*To*: mathgroup at smc.vnet.net*Subject*: [mg87892] Re: Why isn't Expand[] grouping terms by order?*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Sat, 19 Apr 2008 03:37:03 -0400 (EDT)*Organization*: The Open University, Milton Keynes, UK*References*: <fu9fq7$cbn$1@smc.vnet.net>

p at dirac.org wrote: > Consider this: > > In[19]:= Expand[ (1+a*x)*(1+b*x), x] > > 2 > Out[19]= 1 + a x + b x + a b x > > > How can I coax Mathematica to give me this, instead: > > 2 > Want[19]= 1 + (a + b) x + a b x > > Why isn't Mathematica reporting the answer in terms of powers of x? The function *Collect[]* is what you are looking for. In[1]:= Collect[(1 + a*x)*(1 + b*x), x] Out[1]= 1 + (a + b) x + a b x^2 In[2]:= Expand[(1 + a*x)*(1 + b*x), x] Out[2]= 1 + a x + b x + a b x^2 In[3]:= Collect[%, x] Out[3]= 1 + (a + b) x + a b x^2 Regards, -- Jean-Marc