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)

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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