If √a+ib = x+iy, then possible value of √a+ib is
√a+ib = x+iy ⇒ (√(a+ib))2 =(x+iy)2
⇒ a=x2-y2, b=2xy And hence
√a−ib =√x2−y3−2xyi=√(x+yi)2 = x-iy
Note: In the question, it should have been given that a,b,x,y belongs to R.