SOLUTION: (4+5i)(2-3i)

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Question 283669: (4+5i)(2-3i)
Found 2 solutions by oberobic, PRMath:
Answer by oberobic(2304) About Me  (Show Source):
Answer by PRMath(133) About Me  (Show Source):
You can put this solution on YOUR website!
(4+5i)(2-3i)


Use FOIL (first outside inside last)


First: 4+%2A+2+=+8
Outside: 4+%2A+%28-3i%29+=+-12i
Inside: %285i%29+%2A+2+=+10i
Last: 5i+%2A+%28-3i%29+=+-15i%5E2

Let's put it all together: 8+-+12i+%2B+10i+-15i%5E2
Combine like terms: 8+-2i+-+15i%5E2


We're not done yet. See the -15i%5E2?
Well, i%5E2 = -1

Therefore, for -15i%5E2 you really have: %28-15%29%28-1%29 which is: 15

THEREFORE... you really have 8 - 2i + 15, which is.....
23 - 2i


See how that worked out? I hope this helps you. :-)