Does anyone know exactly how/when Solver uses the parameter constraints?
When I ask Solver to find the value of x for which f(x)=0 subject to the
constraints that x=L and x<=U, I always assumed that Solver would never try
to evaluate f(x) at values of x outside of the interval (L,U), but that
assumption turns out to be false!

For example, with
A1 = -1928199651581/72909355965555
B1 = -1442943051207/607577966379625
C1 = -43172037099106/5468201697416620
A2 = 5E-12
B2 = (A$1+B$1*LOG(A2))/(1+C$1*LOG(A2))
When I ask Solver to set B2 equal to zero by changing A2 subject to the
constraints that A2<=1E-11 and A2=1E-12, then Solver encounters an error and
terminates
with A2 = -0.000000099995. Why was Solver even considering negative values
of A2?

Note that my question is about the operation of Solver with constraints, not
how
to find the root of this particular function. If I parameterize B2 as a
function of
LOG(A2) instead of a function of A2, then Solver will converge to a solution
with this function, but my concern is how to have constraints respected in
more complicated situations.

My testing was specifically in Excel 2003. I have not been able to get
Solver to install properly in the 2007 demo, possibly because I had earlier
run 2007 beta on that machine, though I did uninstall the beta before
installing the production demo.

Jerry