General functional notation (e.g. f(x) ) is not supported. If you wish to draw a function such as f(x) = x2, replace f(x) with y (or any other unused variable).

So in your case you need to type in the expression:
4*(-1)^2-3*(-1)+2​​​ and click on "Solve"

Ths way you will find that f(-1) = 9.

Click here to see the step by step calculation.