For all complex numbers z of the form 1 + i α ,   α ∈ R , if z 2 = x + i y , then

For all complex numbers z of the form 1+iα, αR, if z2=x+iy, then 
  1. y2-4x+4=0
  2. y2+4x-4=0
  3. y2-4x+2=0
  4. y2+4x+2=0

Solution

Given z=1+, z2=x+iy

1+2=x+iy

12+i2α2+2iα=x+iy

Using i2=-1,

1-α2+2iα=x+iy

Equating the real and imaginary parts, we get

x=1-α2 and y=2α

α2=1-x and y2=4α2

y2=41-x

y2=4-4x

y2+4x-4=0.

Asked in: JEE Main 2014 (19 Apr Online)

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