This we can very simply go through directly. ((a+ib)(a-ib))-((-c+id)(c+id)). ⇒ (a 2 +b 2 )-(-c 2 -d 2 ). ⇒ a 2 +b 2 + c 2 +d 2 ∵ i × i=-1

Evaluate

This we can very simply go through directly.

((a+ib)(a-ib))-((-c+id)(c+id)).

⇒ (a²+b²)-(-c² -d²).

⇒ a²+b² + c²+d²

∵ i × i=-1