Question

Evaluate 15 i^3 - 20 i^2. 25 POINTS!!!!!!!! NEED ANSWER NOW!!!!! BRAINLIEST

Answer 1

If i³ = -i and i² = -1 substitute these values into the expression

= (15 * -i) - (20 * -1)

= -15i - (-20)

= -15i + 20

Answer 2

Answer:

$\boxed{\bold{-15i+20}}$

Step-by-step explanation:

$\bold{15i^3: \ -15i}$

$\bold{-15i-20i^2}$

$\bold{20i^2: \ -20}$

$\bold{-15i-\left(-20\right)}$

Apply rule $\bold{-\left(-a\right)=a}$

$\bold{-15i+20}$

- M