Answer/Step-by-step explanation:
There are four multiplications you have to do to times these together.
If you have learned how to multiply something like this:
(x + 3)(x - 3)
it will be done in the same way.
(Actually, also there's a short cut called Difference of Two Squares or Difference of Perfect Squares)
Here are the
four multiplications:
8×8 = 64
8 × 4i = 32i
-4i × 8 = -32i
-4i × 4i = -16i^2
Some people use an area model to multiply these or algorithm called FOIL.
So, the two middle multiplications add up to zero and just like, zero out each other 32i + -32i is just nothing, zero.
Then you are left with the first and last terms.
64 + (-16i^2)
REMEMBER:
i^2 = -1
64 + (-16)(-1)
= 64 + 16
= 80