The least value of |z| where z
Question:

The least value of $|z|$ where $z$ is complex number which satisfies the inequality

$\exp \left(\frac{(|z|+3)(|z|-1)}{|| z|+1|} \log _{e} 2\right) \geq \log _{\sqrt{2}}|5 \sqrt{7}+9 i|$

$\mathrm{i}=\sqrt{-1}$, is equal to :

  1. (1) 3

  2. (2) $\sqrt{5}$

  3. (3) 2

  4. (4) 8


Correct Option: 1

Solution:

$\exp \left(\frac{(|z|+3)(|z|-1)}{|| z|+1|} \ln 2\right) \geq \log _{\sqrt{2}}|5 \sqrt{7}+9 i|$

$\Rightarrow 2^{\frac{(|z|+3)||||-1)}{(|z|+1)} \geq \log _{\sqrt{2}}(16)}$

$\Rightarrow 2^{\frac{(|z|+3)(|| \mid-1)}{(\mid z+1)} \geq 2^{3}}$

$\Rightarrow \frac{(|z|+3)(|z|-1)}{(|z|+1)} \geq 3$

$\Rightarrow(|z|+3)(|z|-1) \geq 3(|z|+1)$

$\Rightarrow|z|^{2}+|z|-6 \geq 0$

$\Rightarrow(|z|-3)(|z|+2) \geq 0 \Rightarrow|z|-3 \geq 0$

$\Rightarrow|z| \geq 3 \quad \Rightarrow|z|_{\min }=3$

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