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MathGroup Archive 2000

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Re: just doesn't work

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25363] Re: [mg25346] just doesn't work
  • From: BobHanlon at aol.com
  • Date: Sun, 24 Sep 2000 03:01:31 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 9/23/2000 3:59:53 AM, justmyname at email.si writes:

>I am writing a paper in Mathematica 4.0, and I found it to be very powerful
>text editor. However, I encountered some deadly problems, which I cannot
>solve. Thanks for any help!
>
>1. How can I replace a symbol m with (4 a b c Pi Ro)/3 in expr
>
>(4 a^3 b c K Pi Ro)/(15 r^3)
>
>expr/.(4 a b c Pi Ro)/3 -> m
>just doesn't work
>
>
>2. How Can I 'bring out' a defined part from a sum of two terms.
>
>e.g.
>
>Bo[a^2 b c + a b c,a b c] - (would produce) - > a b c (a+1)
>
>Collect[expr,{a,b,c}]
>just doesn't work.
>

1. Substitute for either b, c, or Ro. Showing that each substitution provides 
the same result

(4 a^3 b c K Pi Ro)/(15 r^3) /. (Solve[(4 a b c Pi Ro)/3 == m, #] // 
          Flatten) & /@ {b, c, Ro} // Union

{(a^2*K*m)/(5*r^3)}

2. Use Simplify

a^2 b c + a b c // Simplify

a*(1 + a)*b*c


Bob Hanlon


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