Author 
Comment/Response 
Karin

08/30/99 07:58am
I have a function f(x) that I want to minimize. I therefore take the derivative of f with respect to x, set it to 0 and
solve for x.
Solve[D[f,x]==0,x]
Say that gives me xopt=1/y+1 where y is a (symbolic)
constant. Now I need to make sure that xopt is within the
boundaries of possible values of x. Say that xy<1 is the
only constraint I have. In version 3 I can't use
InequalitySolve[xy<1,x] since xy<1 is not a ''formula
constructed with univariate polynomial equations and
inequalities in x''. I assume that is because Mathematica
doesn't know if y is less than or greater than 0.
My question is therefore would Mathematica 4 be able to
solve this problem for me given that I know y is positive?
Maybe with InequalitySolve[xy<1,y>0,x] i.e. with the added
assumption that y is greater than 0? Is there another way
of solving this problem? (Solve[xy==1,x] doesn't help me
since I only get the boundary valuie x=1/y as ananswer. I
still don't know if 1/y+1 is inside the boundaries or
not...)
Thanks for any help,
Karin
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