Which method would best verify if an arbitrary function f(x) is even, odd, or neither based on its algebraic expression?
1) Differentiating the function and checking if f(-x) = -f(x)
2) Integrating the function and checking if f(-x) = f(x)
3) Substituting x = -x in the function and checking if f(-x) = f(x)
4) Finding the derivative of the function and checking if f(-x) = f(x)