If x−iy=√a−idc−id, prove that (x2+y2)2=a2+b2c2+d2.
Here x−iy=√a−idc−id
Squaring both sides, we get
(x−iy)2=a−ibc−id
⇒ |(x−iy)2|=∣∣a−ibc−id∣∣
⇒ |x−iy||x−iy|=|a−ib||c−id|
⇒ (√x2+y2)(√x2+y2)=√a2+b2√c2+d2
⇒ (x2+y2)=√a2+b2c2+d2
Squaring both sides
(x2+y2)2=a2+b2c2+d2