       Some Easy (hopefully) Questions

• To: mathgroup at christensen.cybernetics.net
• Subject: [mg2030] Some Easy (hopefully) Questions
• Date: Sat, 16 Sep 1995 01:40:17 -0400
• Organization: Duke University, Durham, NC, USA

```I'm trying to run a model using Mathematica. I've scoured all our
libraries and all the books are gone. Working with all too basic
Mathematica By Example, I haven't been able to find how to do some rather
easy things.

The first thing I want to do is find a max (I need to plug the max and
where it occurs into anther equation). I have a function, and I have
taken both the first and second derivatives. I solve for f'(x) = 0. But
here's where the trouble comes in. I want to plug these points back into
my f(x). How can I do this. Look at the following example:

possmax = Solve[(x - 1)^2 == 0,x] // N

I get {{x -> 1.},{x ->1.}}
and when I try

possmax[]

I get {x ->1.}

but I want the number 1 instead.

I know this if probably extremely basic, but due to lack of available
documentation here, I can not figure it out.

P.S. another useful trick to know would be how many objects are in a
list. My function a bit more complicated (compositions, logs etc.), and I
don't exactly how many solutions I will have from the Solve[ ] statement.

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