If a complex number $z$ statisfies the equation $x+\sqrt{2}|z+1|+i=0$, then $|z|$ is equal to :

If a complex number $z$ statisfies the equation $x+\sqrt{2}|z+1|+i=0$, then $|z|$ is equal to :
  1. 2
  2. $\sqrt{3}$
  3. $\sqrt{5}$
  4. 1

Solution

Given equation is $ \begin{aligned} & z+\sqrt{2}|z+1|+i=0 \\ & \text { put } z=x+i y \text { in the given equation. } \\ & (x+i y)+\sqrt{2}|x+i y+1|+i=0 \\ & \Rightarrow x+i y+\sqrt{2}\left[\sqrt{(x+1)^2+y^2}\right]+i=0 \end{aligned} $ Now, equating real and imaginary part, we get $ \begin{aligned} & x+\sqrt{2} \sqrt{(x+1)^2+y^2}=0 \text { and } \\ & y+1=0 \Rightarrow y=-1 \\ & \Rightarrow x+\sqrt{2} \sqrt{(x+1)^2+(-1)^2}=0 \\ & \Rightarrow \sqrt{2} \sqrt{(x+1)^2+1}=-x \\ & \Rightarrow 2\left[(x+1)^2+1\right]=x^2 \\ & \Rightarrow x^2+4 x+4=0 \\ & \Rightarrow x=-2 \end{aligned} $ Thus, $z=-2+i(-1) \Rightarrow|z|=\sqrt{5}$

Asked in: JEE Main 2013 (22 Apr Online)

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