Answer:
-45i² - 213i + 60
Explanation:
Use the FOIL method to find the answer. It stands for:
First: multiply the first number of each binomial
Outside: multiply the outside numbers of each binomial (number that has no number of 1 side of it)
Inside: multiply the 2 inside numbers
Last: multiply the last numbers of each binomial.
Now, to plug in the numbers:
First: 15 × 4 = 60
Outside: 15 × -15i = -225i
Inside: 3i × 4 = 12i
Last: 3i × -15i = -45i²
Now, you add them all together in an equation.
60 - 225i + 12i - 45i²
Highest exponent should go first, then variable, then no variable
-45i² -225i + 12i + 60
Combine like terms.
-45i² - 213i + 60
Hope this helps!