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MathGroup Archive 2006

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RE: Is mathematica able to transform formula

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71879] RE: [mg71864] Is mathematica able to transform formula
  • From: "David Park" <djmp at earthlink.net>
  • Date: Sat, 2 Dec 2006 05:10:45 -0500 (EST)

pujo,

Do you mean that you want to do it in steps, like one might do it by hand?
Then you could use the following.

eqn1 = f == a b + 5;
eqn2 = c == a b;

Inner[Subtract, eqn1, eqn2, Equal]
# + c & /@ %						giving
-c + f == 5
f == 5 + c

We first subtracted the two equations, and then used a pure function to add
c to both sides. If you wanted a more complicated combination of the two
equations, say 2 times the first equation minus three times the second
equation, then you could use a pure function in the Inner command rather
than Subtract. 2 #1 - 3 #2&.

You could also do it using Solve

Equal @@ Part[Solve[{eqn1, eqn2}, f, a], 1, 1]
f == 5 + c

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/


From: ajikoe at gmail.com [mailto:ajikoe at gmail.com]

Hello,

I have a question:
if I have a symbolic expression:
f  = a * b + 5
c = a * b

Can Mathematica builds f = c + 5 for me ?


Sincerely Yours,
pujo



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