Hello from MrBillDoesMath!
Answer:
4 (d + 2i) (d -2i)
Discussion:
Factor the value 4 from each term to get
4d^2 + 16 = 4 (d^2+4)
d^2+4 factors over the set of complex numbers into (d-2i)(d+2i)
where i = square root of (-1)
Thank you,
MrB
