Hello there!
We must set up this equation to find a * b.
We know:
a = 7i - 4j
b = 4i + 3j
(7i - 4j)(4i + 3j)
Let's use FOIL
First
Outside
Inside
Last
First: 7i * 4i
Outside: 7i * 3j
Inside: -4j * 4i
Last: -4j * 3j
7i * 4i = 28i^2
7i * 3j = 21ij
-4j * 4i = -16ij
-4j * 3j = -12j^2
28i^2 + 21ij - 16ij - 12j^2
Now we must simplify
21ij - 16ij =5ij
28i^2 - 12j^2 + 5ij
Your answer is 28i^2 - 12j^2 + 5ij
I hope my answer helped you!
~ Fire
