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JEE Main 202227 JuneEvening Shift
Exam
JEE Main
Year
2022
Date
27 June
Shift
Evening Shift
Subject
Mathematics
Chapter
Complex Number

JEE Main 2022 · 27 June · Evening Shift · Mathematics · Complex Number

Let for some real numbers α and β, a = α - iβ . If the system of...

Let for some real numbers α\alpha and β,a=α−iβ\beta, a = \alpha - i\beta. If the system of equations 4ix+(1+i)y=04ix + \left(1 + i\right)y = 0 and 8(cos2π3+isin2π3)x+a¯y=08\left(cos\dfrac{2\pi}{3} + isin\dfrac{2\pi}{3}\right)x + \overset{¯}{a}y = 0 has more than one solution then αβ\dfrac{\alpha}{\beta} is equal to

Options

  1. A2−32 - \sqrt{3}
  2. B2+32 + \sqrt{3}
  3. C−2+3- 2 + \sqrt{3}
  4. D−2−3- 2 - \sqrt{3}

Correct answer

A. 2−32 - \sqrt{3}

Step-by-step solution

The given system of equations has more than one solution, then it must have infinitely many solutions.

So, 4i8(cos2π3+isin2π3)=1+iα+iβ\dfrac{4i}{8\left(cos\dfrac{2\pi}{3} + isin\dfrac{2\pi}{3}\right)} = \dfrac{1 + i}{\alpha + i\beta} \left(∵ {a=α−iβ⇒a=α+iβ\begin{cases}a & = \alpha - i\beta \\ ⇒ a & = \alpha + i\beta\end{cases}\right)</p><p></p><p>⇒ \dfrac{4i}{8\left(\dfrac{- 1}{2} + i\dfrac{\sqrt{3}}{2}\right)} = \dfrac{1 + i}{\alpha + i\beta}</p><p></p><p>⇒ \alphai - \beta = - 1 - i + \sqrt{3}i - \sqrt{3}</p><p></p><p>⇒ - \beta + \alphai = \left(- 1 - \sqrt{3}\right) + \left(- 1 + \sqrt{3}\right)i</p><p></p><p>⇒ \alpha = - 1 + \sqrt{3}&- \beta = - 1 - \sqrt{3}</p><p></p><p>∴ \dfrac{\alpha}{\beta} = \dfrac{- 1 + \sqrt{3}}{1 + \sqrt{3}}$=−1+31+3×1−31−3= \dfrac{- 1 + \sqrt{3}}{1 + \sqrt{3}} \times \dfrac{1 - \sqrt{3}}{1 - \sqrt{3}}

=−(1−3)21−3=1+3−232=2−3= \dfrac{- {\left(1 - \sqrt{3}\right)}^{2}}{1 - 3} = \dfrac{1 + 3 - 2\sqrt{3}}{2} = 2 - \sqrt{3}

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