What is the limit of the polynomial function f(x) = x^3 - 2x^2 + x - 5 as x approaches 2?

Under what condition can direct substitution be used to find the limit of a rational function?

Find the limit of the function f(x) = (x^2 - 4) / (x - 2) as x approaches 2.

Evaluate the limit of the function f(x) = (sqrt(x) - 2) / (x - 4) as x approaches 4.

Find the limit of the function f(x) = (x^3 - 8) / (x^2 - 4) as x approaches 2.