# Function Notation Help!

I am trying to transcribe some inverse function activities into Desmos. Some of the questions require function notation, specifically evaluating f(x) as an input of output x.

I haven’t found a way to evaluate this effectively. differenceFunction doesn’t appear to recognize ‘f(x)’ as a variable. I was wondering if there is a solution that I am not thinking of that would allow an inverse equation to be evaluated with f(x) as input?

My current workaround is to assign a single variable, but that diminishes an important aspect of the lesson.

Can you be more specific about what you’re trying to evaluate? Is it from student input? If so, what is the input you want to see from students to evaluate?

You’re correct that differenceFunction won’t accept ‘f(x)’ as a variable, but it should evaluate a function in terms of x with f(x) as a variable within it. For example, Desmos calculator will graph both of these functions.

f(x)=2x+5
g(x)=\frac{f(x)-5}{2}


Thanks Daniel,

For the problems set that I’m looking at the student has to create an inverse function with f(x) as an input. For example, in the math input latex, they would x=(g(x)+4)/7 - I know that I could try to come up with all of the latex solutions possible, but would prefer something as elegant as parseEquation where I can set the equality and any correct inverse equation would show as correct.

Sorry I didn’t reply to this. Did you see my Function notation workaround? If you wanted g(x), you’d need to change the parameters from f to g in both the graph CL and the graph itself.