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Re: FullSimplify fails for very large numbers and powers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89934] Re: [mg89880] FullSimplify fails for very large numbers and powers
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Wed, 25 Jun 2008 06:22:29 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

expr1 = (-\
1505046085600344525396741688335403635402237542400000000000000000000000\
000*(-kt h + 2*k*r)^187*(kth - 2*k*r + 6*s*(-2*k*rho + s))^6*(kth - 
        2*k*r + 8*
         s*(-2*k*rho + 
           s))^6*((k^196*(kth + 
            s^2))/(301009217120068905079348337667080727080447508480000\
0000000000000000000000*(-kth + 2*k*r)^187*(kth - 2*k*r + 
             6*s*(-2*k*rho + s))^6*(kth - 2*k*r + 
             8*s*(-2*k*rho + s))^6) + (k^196*(4*k^2 - 4*k*rho*s + 
            s^2))/(301009217120068905079348337667080727080447508480000\
0000000000000000000000*(-kth + 2*k*r)^187*(kth - 2*k*r + 
             6*s*(-2*k*rho + s))^6*(kth - 2*k*r + 
             8*s*(-2*k*rho + s))^6)))/k^199;

expr2 = expr1 // Together

-(((2*k*r - h*kt)^187*(4*k^2 - 4*rho*s*k + 2*s^2 + kth))/(2*
     k^3*(2*k*r - kth)^187))

expr1 == expr2 // Simplify

True

Simplify[expr2, h*kt == kth]

-((4*k^2 - 4*rho*s*k + 2*s^2 + kth)/(2*k^3))


Bob Hanlon

---- Paul Schneider <a9408266 at unet.univie.ac.at> wrote: 
> Dear newsgroup,
> 
> FullSimplify (Mathematica 6 and 5.2) does not simplify the expression:
> 
> (-1505046085600344525396741688335403635402237542400000000000000000000000000*(-kth 
> + 2*k*r)^187*(kth - 2*k*r + 6*s*(-2*k*rho + s))^6*
>    (kth - 2*k*r + 8*s*(-2*k*rho + s))^6*((k^196*(kth + 
> s^2))/(3010092171200689050793483376670807270804475084800000000000000000000000000*(-kth 
> + 2*k*r)^187*
>       (kth - 2*k*r + 6*s*(-2*k*rho + s))^6*(kth - 2*k*r + 8*s*(-2*k*rho 
> + s))^6) + (k^196*(4*k^2 - 4*k*rho*s + s^2))/
>  
> (3010092171200689050793483376670807270804475084800000000000000000000000000*(-kth 
> + 2*k*r)^187*(kth - 2*k*r + 6*s*(-2*k*rho + s))^6*
>       (kth - 2*k*r + 8*s*(-2*k*rho + s))^6)))/k^199
> 
> to the much nicer
> 
> -(4*k^2 + kth - 4*k*rho*s + 2*s^2)/(2*k^3)
> 
> Do you have tips on how I could achieve this?
> 
> Thank you,
> 
> Paul
> 
> PS: the expressions are in InputForm. Somehow the power signs get lost 
> when pasting from Thunderbird. Pasting from Kmail seems to work.
> 



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