(6 - 4i)²
use square of difference;
6² - 2 × 6 × 4i + (4i)²
use multiplication distributive property;
36 - 2 × 6 × 4i + 4²i²
36 - 2 × 6 × 4i + 16i²
36 - 2 × 6 × 4i + 16 × -1
36 - 48i + 16 × -1
36 - 48i - 16
(36 - 16) - 48i
20 - 48i
hope that helps, God bless!
