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MathGroup Archive 1998

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Re: Simplify

  • To: mathgroup at smc.vnet.net
  • Subject: [mg14808] Re: [mg14780] Simplify
  • From: BobHanlon at aol.com
  • Date: Wed, 18 Nov 1998 01:29:09 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 11/14/98 7:11:34 AM, jtischer at col2.telecom.com.co
writes:

>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.
>

Jurgen,

a = (-7253*2^(1 + 2*n)*5^n - 523*4^n*5^(1 + n) + 17121*20^n + 
    130321*20^n*n^4)/130321;

b = FullSimplify[a]

(-(5^n*(7253*2^(1 + 2*n) + 2615*4^n)) + 20^n*(17121 + 130321*n^4))/
  130321

b = b /. {5^n -> m, 20^n -> 4^n*m}

(-((7253*2^(1 + 2*n) + 2615*4^n)*m) + 4^n*m*(17121 + 130321*n^4))/
  130321

b = Simplify[b]

4^n*m*n^4

b = b /. m -> 5^n

20^n*n^4

FullSimplify[a/b]

1


Bob Hanlon


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