Question

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

Answer 1

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