Answer:
B
Step-by-step explanation:
Expanding the products using FOIL , noting that i² = - 1
A
(2x - 4i)(x - 2i)
= 2x² - 4ix - 4ix + 8i²
= 2x² - 8ix - 8 ≠ 2x² + 8
B
(2x - 4i)(x + 2i)
= 2x² + 4ix - 4ix - 8i²
= 2x² + 8 ← True
C
(2x - 2i)(x + 6i)
= 2x² + 12ix - 2ix - 12i²
= 2x² + 10ix + 12 ≠ 2x² + 8
D
(2x + 4i)(x + 2i)
= 2x² + 4ix + 4ix + 8i²
= 2x² + 8ix - 8 ≠ 2x² + 8
Thus
(2x - 4i)(x + 2i) = 2x² + 8 → B
