If f (x) = x3 - 2x2, which expression is equivalent to f (i) ?

We have to find f (i) for the function: f (x) = x³ - 2 x²

f (i) = i³ - 2 i²

We know that: i² = - 1 and i³ = - i

f (i) = - i - 2 · ( - 1)

f (i) = - i + 2

The complex number is written in form: z = a + b i

Answer:

f (i) = 2 - i