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Re: why does it still running?!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113162] Re: why does it still running?!
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 16 Oct 2010 13:10:27 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

Works fine on my system

$Version

"7.0 for Mac OS X x86 (64-bit) (February 19, 2009)"

eqns = ((1 - a)*x - b)/a^(i/1) ==
    ((1 - a)*y - b)/a^(j/1) &&
   
   j == 10;

Timing[soln = {Reduce[eqns, {y},
     Backsubstitution -> True] //
    ToRules}]

{0.312331, {{j -> 10, a -> 1, b -> 0}, {j -> 10, 
   y -> -((a^-i (-a^10 b + a^i b + a^10 x - a^11 x))/(-1 + a))}, {j ->
     10, a -> 1}}}

eqns /. soln // Simplify

{True, True, True}


Bob Hanlon

---- olfa <olfa.mraihi at yahoo.fr> wrote: 

=============
Hi Mathematica community,
why Mathematica still running and so can't give me a solution for this system
Reduce[
((1 - a)*x - b)/a^(i/1) == ((1 - a)*y - b)/a^(j/1) && j == 10,{y},
Backsubstitution -> True]

Thank you very much.




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