Question

simplify.
(5 + 3i)3i
write your answer in the form a + bi.

Explanation:

Step1: Distribute $3i$ to terms

$(5 + 3i)3i = 5\cdot3i + 3i\cdot3i$

Step2: Compute each product

$= 15i + 9i^2$

Step3: Substitute $i^2=-1$

$= 15i + 9(-1) = -9 + 15i$

Answer:

$\boldsymbol{-9 + 15i}$