Re: Solve problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg98041] Re: [mg97988] Solve problem*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Sat, 28 Mar 2009 05:45:43 -0500 (EST)*Reply-to*: hanlonr at cox.net

a1 /. Select[{{b1 -> -2, a1 -> -1}, {b1 -> 0.5, a1 -> 3}}, (a1 /. #) > 0 &] {3} Cases[{{b1 -> -2, a1 -> -1}, {b1 -> 0.5, a1 -> 3}}, (a1 -> x_ /; x > 0) :> x, Infinity] {3} Or instead of using Solve use Reduce and include constraint on a1 Bob Hanlon ---- Bruno Campanini <BC at gmail.com> wrote: ============= I have a Solve[...] which gives me solutions like {{b1 -> -2, a1 -> -1 }, {b1 -> 0.5, a1 -> 3}} or like {{a1 -> 1, b1 -> 3}} How can I get the positive value for a1, which is 3 in the first case and 1 in the second one? Bruno