Easy MCQ +4 / -1 PYQ · JEE Mains 2020

Let z = x + iy be a non-zero complex number such that ${z^2} = i{\left| z \right|^2}$, where i = $\sqrt { - 1}$ , then z lies on the :

  1. A line, y = –x
  2. B real axis
  3. C line, y = x Correct answer
  4. D imaginary axis

Solution

Given z = x + iy <br><br>and ${z^2} = i{\left| z \right|^2}$ <br><br>$\Rightarrow$ (x + iy)<sup>2</sup> = i(x<sup>2</sup> + y<sup>2</sup>) <br><br>$\Rightarrow$ x<sup>2</sup> - y<sup>2</sup> + 2ixy = i(x<sup>2</sup> + y<sup>2</sup>) + 0 <br><br>Comparing both side we get, <br><br>x<sup>2</sup> - y<sup>2</sup> = 0 <br><br>$\Rightarrow$ x<sup>2</sup> = y<sup>2</sup> <br><br>and 2xy = (x<sup>2</sup> + y<sup>2</sup>) <br><br>$\Rightarrow$ (x - y)<sup>2</sup> = 0 <br><br>$\Rightarrow$ x = y <br><br>$\therefore$ z lies on line x = y

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 →