Let a,b∈R and a2+b2=0 .
Suppose S={z∈C:z=a+ibt1,t∈R,t=0} , where
i=−1 . If z=x+iy and z∈S , then (x,y) lies on
a. the circle with radius 2a1 and centre (2a1,0) for a>0,b=0
b. the circle with radius −2a1 and centre (−2a1,0) for a<0,b=0
c. the X -axis for a=0,b=0
d. the Y -axis for a=0,b=0