%%

Let for some real numbers $$\alpha$$ and $$\beta$$, $$a = \alpha - i\beta $$. If the system of equations $$4ix + (1 + i)y = 0$$ and $$8\left( {\cos {{2\pi } \over 3} + i\sin {{2\pi } \over 3}} \right)x + \overline a y = 0$$ has more than one solution, then $${\alpha \over \beta }$$ is equal to

JEE · Math · previous-year question

  1. A.$$ - 2\sqrt 3 $$
  2. B.$$2 - \sqrt 3 $$correct
  3. C.$$2 + \sqrt 3 $$
  4. D.$$ - 2 - \sqrt 3 $$

Answer

B. $$2 - \sqrt 3 $$

Explanation

Given $$a = \alpha - i\beta $$ and $$4ix + (1 + i)y = 0$$ ...... (i) $$8\left( {\cos {{2\pi } \over 3} + i\sin {{2\pi } \over 3}} \right)x + \overline a y = 0$$ .... (ii) By (i) $${x \over y} = {{ - (1 + i)} \over {4i}}$$ ...... (iii) By (ii) $${x \over y} = {{ - \overline a } \over {8\left( {{{ - 1} \over 2} + {{\sqrt 3 i} \over 2}} \right)}}$$ ..... (iv) Now by (iii) and (iv) $${{1 + i} \over {4i}} = {{\overline a } \over {4\left( { - 1 + \sqrt 3 i} \right)}}$$ $$ \Rightarrow \overline a = \left( {\sqrt 3 - 1} \right) + \left( {\sqrt 3 + 1} \right)i$$ $$ \Rightarrow \alpha + i\beta = \left( {\sqrt 3 - 1} \right) + \left( {\sqrt 3 + 1} \right)i$$ $$\therefore$$ $${\alpha \over \beta } = {{\sqrt 3 - 1} \over {\sqrt 3 + 1}} = 2 - \sqrt 3 $$

Practice more JEE questions

Answer thousands more real JEE previous-year questions free, get graded instantly, and climb the global ranked leaderboard.

Practice JEE free →

More JEE Math questions