If \(\alpha+i \beta\) and \(\gamma+i \delta\) are the roots of \(x^2-(3-2 i) x-(2 i-2)=0, i=\sqrt{-1}\), then \(\alpha \…
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If \(\alpha+i \beta\) and \(\gamma+i \delta\) are the roots of \(x^2-(3-2 i) x-(2 i-2)=0, i=\sqrt{-1}\), then \(\alpha \gamma+\beta \delta\) is equal to :
[JEE Main 2025, 28 Jan (Shift 2)]
✓ Correct answer: d)
2
Explanation
\({x}^{2}-\left(3-2i\right)x-\left(2i-2\right)=0\)
\(x=\frac{(3-2i)\pm \sqrt{(3-2i{)}^{2}-4(1)(-(2i-2))}}{2(1)}\)
\(x=\frac{3-2i\pm \sqrt{-3-4i}}{2}\)
\(=\frac{3-2\mathrm{i}\pm \sqrt{(1{)}^{2}+(2\mathrm{i}{)}^{2}-2(1)(2\mathrm{i})}}{2}\)
\(=\frac{3-2\mathrm{i}\pm (1-2\mathrm{i})}{2}\)
\(x=\frac{3-2\mathrm{i}+1-2\mathrm{i}}{2},\frac{3-2i-1+2i}{2}\)
\(x=2–2i,1+0i\)
So \(\alpha \gamma +\beta \delta =2\left(1\right)+\left(-2\right)\left(0\right)=2\)
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