I want to find the x-value of a function.

I found is the use of the SOLVE equation to develop an equation.

If anyone can help me I would appreciate it.

thank you

File not found.File not found.

Jean's reply doesn't solve anything.
He directly gave the result.
If variables change, his sheet won't work.

This file is the real solution for your function.
Q202303131118_solved.sm (24 KiB) downloaded 40 time(s).

Here a quick explanation for your problem.
erf() function doesn't like near all solvers.
Unknowns(f(x)) should give x as result.



But because erf(), Unknowns() gives nothing.
Thus solvers can't find a variable to start.
Except al_nleqsolve() as you can see.



You can write your own bisection algorithm too.
It will give the result, will take longer than al_nleqsolve()



Yet it works too.



Regards

roots Dichotomy is Grand Doctor ... dates back Mathcad 8 Pro.
You should be able to adapt wrt other project parameters.
Offered as guide line. For +, please don't hesitate.
Cheers Jean.

Solve Dichotomy f(x)-u Forum Copy.sm (49 KiB) downloaded 21 time(s).

... added automated search point of inversion.
Cheers Jean.

Solve Dichotomy f(x)-u Forum Copy.sm (51 KiB) downloaded 27 time(s).