Easy MCQ +4 / -1 PYQ · JEE Mains 2020

The product of the roots of the
equation 9x2 - 18|x| + 5 = 0 is :

  1. A ${{5} \over {9}}$
  2. B ${{5} \over {27}}$
  3. C ${{25} \over {81}}$ Correct answer
  4. D ${{25} \over {9}}$

Solution

$9{x^2} - 18\left| x \right| + 5 = 0$<br><br>$\Rightarrow$ $9{x^2} - 15\left| x \right| - 3\left| x \right| + 5 = 0$ ($\because$ x<sup>2</sup> = ${\left| x \right|^2}$)<br><br>$\Rightarrow$ $3\left| x \right|(3\left| x \right| - 5) - (3\left| x \right| - 5) = 0$<br><br>$\Rightarrow$$\left| x \right| = {1 \over 3},\,{5 \over 3}$<br><br>$\Rightarrow$ $x = \pm {1 \over 3}, \pm \,{5 \over 3}$<br><br>$\therefore$ Product of roots <br><br>= $$\left( \frac{1}{3} \right) \left( -\frac{1}{3} \right) \left( \frac{5}{3} \right) \left( -\frac{5}{3} \right) $$ = ${{25} \over {81}}$

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 →