Hi,

Of course "Solver" wouldn't have any difficulty in finding the x- and
y- values of the intersection point of f(x) and g(x) (by making the
difference between the functions equal zero). However, please note that the
solver solution is a one-time result, and doesn't automatically update when
f(x) and g(x) change; so your have to manually invoke Solver every time the
functions change (I know it is not a big deal, but is certainly an
inconvenience).

The OP did mention, "The curves shift depending on variables that are
read from a spreadsheet........... I can get the curve formulas by graphing
them and requesting the trendline feature, but then I have to manually enter
the curve formulas, set them equal to each other, and solve the equation. Can
Excel do this
automatically from two data sets?".

My purpose of asking the OP for the functional forms of f(x) and g(x)
was that, if both are linear, logarithmic, simple exponential, quadratic, or
power functions (and not higher order polynomials), then the x-value (and
from it, the y-value) of the intersection point can be obtained using
analytical formulas. Since those formulas will reference the cells
containing the parameters/constants of f(x) and g(x), the solutions will
automatically (and conveniently) update when f(x) and g(x) change.

If f(x) and g(x) are higher-order polynomials or if they are of
different functional forms, analytical solutions may be difficult/impossible
to obtain, and "Solver" is the only recourse.

Regards,
B. R. Ramachandran


"Harlan Grove" wrote:

B. R.Ramachandran wrote...
What kind curves are they (i.e., what kind of functions are those trendline
equations) - linear, polynomial, logarithmic, ....? Can you post sample
trendline equations for the pump curve and the system curve?
....

It doesn't matter what kind of curves they are if they're both
functions of a single, common variable (otherwise they couldn't be
graphed together easily). All that's needed is one cell containing the
common X value, one cell for each curve containing the f(x) and g(x)
function values given the common X value and their other respective
parameters, and finally another formula cell calculating the difference
between the two function values. Then use Solver to set that last cell
to zero by changing the X value cell. If the two curve intersect
transversally, Solver shouldn't have any difficulty finding the
intersection point's X value, and both functions will return the same Y
value.

If the two curve intersect nontransversally, e.g., two circles
intersecting at a single point, then Solver might have some difficulty
and the OP would need to play with its options.

"Cadelima" wrote:
I am trying to otain a solution for the number where two curves meet.
Specifically trying to determine the expected flow rate given a pump curve
and system curve. The curves shift depending on variables that are read from
a spreadsheet. I can get the curve formulas by graphing them and requesting
the trendline feature, but then I have to manually enter the curve formulas,
set them equal to each other, and solve the equation. Can Excel do this
automatically from two data sets? Any help would be appreciated.