No solution found - MathCad 14

[djt123]

Can somebody have a look at this?

This uses a solve block and an equation created with a boolean equal to solve for an unknown.
I want to solve for n and for different input values. This works for f := 1 but not f := 2 or f := 3.

I'm not very familiar with MathCad so this may not be the best approach. Any advice would be appreciated.

Regards,
Daniel

 

[rmix22]

The way you had set it up, n has to be an integer (factorials aren't defined for non-integers) and Mathcad isn't good with diophantic equations, to put it polite. Furthermore I guess, you can't expect an integer solution for n anyway - it doesn't exist and thats exactly what Mathcad tells you. You may also simplify and rewrite your equation using Mathcads built-in function for the cumulative binomial distribution "pbinom()" but you won't get a solution either.

In case of your function I was successful replacing the factorials either with the appropriate Gamma functions and also by replacing them using mathcads built-in "combin()". The latter did surprise me as combin() won't work with non-integers, too.
The solution of course is a non-integer and for some reasons beyond me, the symbolic eval would only yield negative solutions (which are correct anyway) for odd values of f and refused to respect a n>0 constraint or an equivalent "assume" statement.
Nevertheless the numeric evaluation, given a positve guess value, always seems to return the prefered positive solution.

 

[djt123]

Many thanks for this!

Your comments are understood and explanation clear. Thanks for providing the updated MathCad file.

Regards,
Daniel