Q. The least positive integer $n$ for which $\left( \frac{1 + i}{1 - i} \right)^{n}$ is real, is

A) 2
B) 4
C) 8
D) None of these
Explanation

(a)
$\frac{1 + i}{1 - i} = \frac{(1 + i)^{2}}{1 - i^{2}} = \frac{2i}{2} = i$
So, $\left( \frac{1 + i}{1 - i} \right)^{n} = (i)^{n}\ \Rightarrow \ n = 2$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.