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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87863] Re: [mg87825] Why isn't Expand[] grouping terms by order?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 19 Apr 2008 03:31:46 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

You are looking for the command Collect

Collect[(1 + a*x)*(1 + b*x), x]

a*b*x^2 + (a + b)*x + 1


Bob Hanlon

---- 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?
> 
> Thanks!
> 



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