If \(z=\frac{1}{2}-2 i\) is such that \(|z+1|=\alpha z+\beta(1+i), i=\sqrt{-1}\) and \(\alpha, \beta \in \mathbb{R}\), t…
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If \(z=\frac{1}{2}-2 i\) is such that \(|z+1|=\alpha z+\beta(1+i), i=\sqrt{-1}\) and \(\alpha, \beta \in \mathbb{R}\), then \(\alpha+\beta\) is equal to
[JEE Main 2024, 29 Jan (Shift 1)]
✓ Correct answer: d)
3
Explanation
Given
\(z=\frac{1}{2}-2 i\)
\(|z+1|=\alpha z+\beta(1+i)\)
\(\left|\frac{3}{2}-2 i\right|=\frac{\alpha}{2}-2 \alpha i+\beta+\beta i\)
\(\left|\frac{3}{2}-2 i\right|=\left(\frac{\alpha}{2}+\beta\right)+(\beta-2 \alpha) i\)
On comparing
\(\beta=2 \alpha\) and \(\frac{\alpha}{2}+\beta=\sqrt{\frac{9}{4}+4}\)
\(\alpha+\beta=3\)
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