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Question

Mathematics Question on Complex Numbers and Quadratic Equations

For all complex numbers z of the form 1 + iα\alpha, α\alpha ϵ\epsilon R, if z = x + iy, then :

A

y24x+2=0y^2 - 4x + 2 = 0

B

y2+4x4=0y^2 + 4x - 4 = 0

C

y24x+4=0y^2 - 4x + 4 = 0

D

y2+4x+2=0y^2 + 4x + 2 = 0

Answer

y2+4x4=0y^2 + 4x - 4 = 0

Explanation

Solution

(1+iα)2=x+iy(1+i \alpha)^{2}=x+i y
1α2+2iα=x+iy1-\alpha^{2}+2 i \alpha= x + i y
so x=1α2,y=2αx=1-\alpha^{2}, y=2 \alpha
putting α=y/2 \alpha= y / 2
x=1(y2)2x=1-\left(\frac{y}{2}\right)^{2}
y2+4x4=0\Rightarrow y^{2}+4 x-4=0