Final answer:
The expression equivalent to f(n) is n³ - 2n².
Step-by-step explanation:
To find the expression that is equivalent to f(n) for the given function f(x) = x³ - 2x², we substitute n in place of x in the function. Thus, f(n) = n³ - 2n².
So, the correct expression is n³ - 2n² which corresponds to option A.