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MathGroup Archive 1998

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Re: Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg14813] Re: Simplify
  • From: "Allan Hayes" <hay at haystack.demon.co.uk>
  • Date: Wed, 18 Nov 1998 01:29:16 -0500
  • References: <72jf7e$3h9@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Jurgen Tischer wrote in message <72jf7e$3h9 at smc.vnet.net>...
>Could someone tell me please how to simplify the following formula?
>
>(-7253*2^(1 + 2*n)*5^n - 523*4^n*5^(1 + n) + 17121*20^n +
>    130321*20^n*n^4)/130321
>
>To my surprise when I changed by hand (with two rules) the powers of 2,
>5 and so on to powers of 20, Mathematica changed them back to this
>form.
>
>Thanks
>
>Jurgen
>
>

Jurgen,

Assuming that you do not want to change n^4 I get

In[70]:=
expr = (-7253*2^(1 + 2*n)*5^n - 523*4^n*5^(1 + n) + 17121*20^n +
          130321*20^n*n^4)/130321 /. {((x_ ^p_) /; x =!= n) -> 20^p}

Out[70]=
(17121*20^n - 523*20^(1 + 2*n) - 7253*20^(1 + 3*n) +
   130321*20^n*n^4)/130321

Allan

---------------------
Allan Hayes
Mathematica Training and Consulting
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565




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