Re: Replace variable in a function

*To*: mathgroup at smc.vnet.net*Subject*: [mg37230] Re: Replace variable in a function*From*: BobHanlon at aol.com*Date*: Thu, 17 Oct 2002 00:09:25 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

In a message dated 10/16/2002 3:05:57 PM, lcfg3 at yahoo.com writes: >I´m new, so I´m sorry if the question is so easy, I really think that >is easy, but I don´t know how to do it. > >I have this: > >b=n-m > >a=x-b > >Y=3a + 4a^2 > >and the program show me this: >3(x-n+m) + 4(x-n+m)^2 > >or, something like that, the problem is that I want the program show >me Y in function of b, or sometimes in function of a, something like >this: > >Y=3(x-b) + 4(x-b)^2 > >or > >Y=3a + 4a^2 > Solve[{b == n - m, a == x - b, Y == 3a + 4a^2}, Y] {{Y -> a*(4*a + 3)}} Solve[{b == n - m, a == x - b, Y == 3a + 4a^2}, Y, a] // FullSimplify {{Y -> (4*b - 4*x - 3)*(b - x)}} Bob Hanlon