How do you multiply #(1+4i)(3+6i)#?

1 Answer
Jade · Daniel L.
Sep 25, 2016

FOIL

Explanation:

Multiply the First terms in each set of parenthesis. #1 xx 3 = 3#
Multiply the Outer terms of each set of parenthesis. #1 xx 6i = 6i#
Multiply the Inner terms of each set of parenthesis. #4i xx 3 = 12i#
Multiply the Last terms in each set of parenthesis.
#4i xx 6i = 24i^2=-24#
First, Outer, Inner, Last - FOIL

So, the answer would be #3 + 6i +12i - 24#
Add like terms: #6i + 12i = 18i# , #3-24=-21#

#(1 + 4i) (3 + 6i)= -21 + 18i#

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