Easy MCQ +4 / -1 PYQ · JEE Mains 2020

If $\alpha$ and $\beta$ are the roots of the equation
2x(2x + 1) = 1, then $\beta$ is equal to :

  1. A $- 2\alpha \left( {\alpha + 1} \right)$ Correct answer
  2. B $2\alpha \left( {\alpha + 1} \right)$
  3. C $2{\alpha ^2}$
  4. D $2\alpha \left( {\alpha - 1} \right)$

Solution

$\alpha$ and $\beta$ are the roots of the equation <br>4x<sup>2</sup> + 2x – 1 = 0. <br><br>$\therefore$ $\alpha$ + $\beta$ = $- {1 \over 2}$ <br><br>$\Rightarrow$ -1 = 2$\alpha$ + 2$\beta$ <br><br>and 4$\alpha$<sup>2</sup> + 2$\alpha$ - 1 = 0 <br><br>$\Rightarrow$ 4$\alpha$<sup>2</sup> + 2$\alpha$ + 2$\alpha$ + 2$\beta$ = 0 <br><br>$\Rightarrow$ $\beta$ = $- 2\alpha \left( {\alpha + 1} \right)$

About this question

Subject: Mathematics · Chapter: Complex Numbers and Quadratic Equations · Topic: Complex Numbers and Argand Plane

This question is part of PrepWiser's free JEE Main question bank. 223 more solved questions on Complex Numbers and Quadratic Equations are available — start with the harder ones if your accuracy is >70%.

Drill 25 more like these. Every day. Free.

PrepWiser turns these solved questions into a daily practice loop. Chapter-wise drills, full mocks, AI doubt chat. No auto-renew.

Start free →