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1)

Let a,b ε R and a2+b20 . Suppose  S=(zϵC:z=1a+ibt,tϵR,t0)  wherei=1 . If z=x+iy and z ε S, then (x,y) lies on


A) the circle with radius 12a and centre (12a,0) for a>0, b0

B) the circle with radius 12a and centre (12a,0) for a<0,b0

C) the X-axis for a0,b=0

D) the Y-axis for a=0,b0

Answer:

Option A,C,D

Explanation:

Here,  x+iy=1a+ibt×aibtaibt

    x+iy=aibta2+b2t2

                    Let                     a≠ 0,b≠ 0

  x=aa2+b2t2 and    y=bta2+b2t2

     yx=btat=aybx

On putting  x=aa2+b2t2, we get

                 x(a2+b2.a2y2b2x2)=a

                    a2(x2+y2)=ax

                    or    x2+y2xa=0     .........(i)

             or         (x12a)2+y2=14a2

  Option (a) is correct.

      For a≠ 0, b=0

x+iy=1ax=1a,y=0

z lies on X-axis

    Option (c) is correct.

For a=0, b≠ 0,

x+iy=1ibt

    x=0, y=1bt

  z lies on Y-axis

  Option (d) is correct