Program that recognizes functions!

Question

I need to do in my school a program that recognizes functions, for example the user will enter x^3-x^2-40, and the x value, they say that I have to separate the operators and the numbers in two stacks, but, what happens if I don't know what the user will input? What the order of the function will be?

Answer 1

use brackets order follows the bodmas rule

Answer 2

use parenthesis