How do you multiply (8-2i)(-3+7i) in trigonometric form?

1 Answer
May 8, 2016

FOIL

Explanation:

If it was (8-2x)(-3+7x)

You would foil, and you would do that same thing.
Now, lets foil with i.

  1. First (8*-3)=-24

  2. Outer (8*7i) = 56i

    • Act i like x
  3. Inner (-2i*-3)=6i

  4. Last (-2i*7i)=-14i^2=-14*-1=14

    • Remember #i^2 = -1

Now put it all back together
-24+56i+6i+14

Combine like terms
-10+62i