SOLUTION: Multipy. Write result in a+bi form. 3i(3+8i) Answers: A) 24+9i B) -15i C) -24+9i D) 17i

Algebra ->  Equations -> SOLUTION: Multipy. Write result in a+bi form. 3i(3+8i) Answers: A) 24+9i B) -15i C) -24+9i D) 17i      Log On


   

Question 146082: Multipy. Write result in a+bi form.
3i(3+8i)
Answers:
A) 24+9i
B) -15i
C) -24+9i
D) 17i
Found 3 solutions by Earlsdon, jim_thompson5910, nerdybill:
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Multply:
3i%283%2B8i%29 Apply the distributive property.
%283i%29%283%29%2B%283i%29%288i%29 Simplify.
9i%2B24i%5E2 Substitute i%5E2+=+-1
9i%2B24%28-1%29 Simplify.
-24%2B9i
Answer C is the choice.

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
3i%283%2B8i%29 Start with the given expression


3i%2A3%2B3i%2A8i Distribute 3i to 3%2B8i


9i%2B24i%5E2 Multiply


9i%2B24%28-1%29 Replace i%5E2 with -1


9i-24 Multiply


-24%2B9i Rearrange the terms

Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
3i(3+8i)
distribute the 3i to each term inside the parenthesis:
(3i)(3)+(3i)(8i)
= (3*3*i) + (3*8*i*i)
= 9i + ((3*8)*(i*i))
= 9i + ((24)*(-1))
= 9i + (-24)
= -24 + 9i