SOLUTION: Please help me solve this problem. (5 + 3i)* (2 + i)

Algebra ->  Functions -> SOLUTION: Please help me solve this problem. (5 + 3i)* (2 + i)      Log On


   

Question 27911: Please help me solve this problem.
(5 + 3i)* (2 + i)
Answer by bmauger(101) About Me  (Show Source):
You can put this solution on YOUR website!
For the most part, you can treat i's just like x's (it's only when we get to i^2 that we have to do anything differently).
So we start by using FOIL to get:
%285%2B3i%29%282%2Bi%29=5%2A2%2B5%2Ai%2B3i%2A2%2B3i%2Ai=10%2B11i%2B3i%5E2
The difference now comes in that i^2 term at the end. Since i is the imaginary number defined by i=sqrt%28-1%29 then i%5E2=-1 so whenever you see an i^2 term, replace it with a negative 1:
10%2B11i%2B3%28-1%29
10%2B11i-3
7%2B11i