If f(x) = x^3 – 2x^2, which expression is equivalent to f(i)?

F(x) = x³ - 2x².

f(i) = i³ - 2i².

i = √-1.

i³ = (√-1)³ = √-1 * √-1 *√-1 = -1*√-1 = -√-1 = -i

i² = (√-1)² = √-1 * √-1  = -1

f(i) = i³ - 2i²  = -i - 2(-1) = -i + 2

f(i) = 2 - i

Where are the functions?