Re: question about maximization with mathematica tool

*To*: mathgroup at smc.vnet.net*Subject*: [mg109412] Re: question about maximization with mathematica tool*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Mon, 26 Apr 2010 04:50:17 -0400 (EDT)

You need to include at least the lower boundary for x expr = FullSimplify[Rationalize[ 12 La*T + (0.12 x + 5 y)*((2 (42 x + 4018 y - 7 x y))/ (9 x y) - (6 x + 574 y - x*y)^2/(2025 x^2 y^2))]]; (Maximize[{expr /. y -> 7/2, 80 <= x < 250}, x] // Simplify) /. r_Rational :> N[r] {12 La T+331.744,{x->80}} (Maximize[{expr /. y -> 2, 80 <= x < 250}, x] // Simplify) /. r_Rational :> N[r] {12 La T+278.921,{x->80}} (Simplify[ Maximize[{expr, 80 <= x < 250, y == 7/2 || y == 2}, x], y == 7/2 || y == 2]) /. r_Rational :> N[r] {Piecewise[ {{12*La*T + 278.9207702469136, y == 2}}, 12*La*T + 331.74427087994457], {x -> 80}} Bob Hanlon ---- MANOLIS <voskakis86 at gmail.com> wrote: ============= i want to maximize the equation below: 12La*T + (0.12x + 5 y)*((2 (42 x + 4018 y - 7 x y))/( 9 x y) - (6 x + 574 y - x y)^2/(2025 x^2 y^2)) it has 4 variables x, y, La, T. I want the maximization for the x variable only. In other words i want to find a relation between x and the other variables that maximizes the whole equation. the restrictions are that 80<x<250 and y==3.5 || y==2 i wrote the command below in mathematica but nothing: Maximize[{12La*T + (0.12x + 5y)*((2 (42 x + 4018 y - 7 x y))/( 9xy) - (6x + 574y - x*y)^2/(2025 x^2 y^2)), x < 250 && x > 80, y == 3.5 || y == 2}, {x}] i dont know why. i dont think that it is the number of variables that causes the problem... thank you very much Manolis