Re: problem with mathematica :(

*To*: mathgroup at smc.vnet.net*Subject*: [mg98572] Re: problem with mathematica :(*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Mon, 13 Apr 2009 03:33:11 -0400 (EDT)*References*: <grs6c7$qjg$1@smc.vnet.net> <49E1AEC9.1090306@gmail.com>

Szabolcs Horv=E1t wrote: > olfa wrote: >> Hi Mathematica community, >> I have this system of equations: >> Reduce[{i >= iP, v + a*t/(1 - d) == vP + a*tP/(1 - d), >> t/d^(x/a) == tP/d^(xP/a), a*i + 1*x == a*iP + 1*xP, >> t/d^(i/-1) == tP/d^(iP/-1), >> z - c*x*(x - a)/(2*a) == zP - c*xP*(xP - a)/(2*a),iP=== 0}, >> {iP,tP,vP,xP,zP},Backsubstitution->True] >> But mathematica still in running until I abort.Could you tell me what >> is the problem? > > Remove the inequality unless you really need it. It makes the problem > much much more difficult. > Actually it looks like you can re-add it once the equation part is solved= : Reduce[{v + (a t)/(1 - d) == vP + (a tP)/(1 - d), t/d^(x/a) == tP/d^(xP/a), a i + 1 x == a iP + 1 xP, t/d^(i/-1) == tP/d^(iP/-1), z - (c x (x - a))/(2 a) == zP - (c xP (xP - a))/(2 a), iP == 0}, {iP, tP, vP, xP, zP}, Backsubstitution -> True] Reduce[% && i >= iP, {iP, tP, vP, xP, zP}, Reals]