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

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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 КиБ) скачан 40 раз(а).

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 КиБ) скачан 21 раз(а).

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

Solve Dichotomy f(x)-u Forum Copy.sm (51 КиБ) скачан 27 раз(а).