Question

(Complex Numbers) Multiply: 2i(-4-i)^2

Answer 1

i = √-1
i^2 = -1
2i ( - 4 - i) (-4 - i)
use foil.
2i(16 + 4i + 4i - i^2)
2i(16+8i - (-1))
2i(17+8i)
34i + 16i^2
34i + 16(-1)
34i -16

Answer 2

Why does the textbook's answer key say -16+30i ? I see how you got 34 though, which is what I would've guessed it is suppose to be.

Answer 3

Yeah, wolfram gave me that too. Idk why.

Answer 4

but my answer is correct..
-i^2 = 1

Answer 5

I think you are right also. I don't see how it would end up with 30i.