Q. If the coefficient of 7th and 13th term in the expansion of ${(1 + x)}^{n}$ are equal, then $n$ is equal to
A) 10
B) 15
C) 18
D) 20
Explanation
(c)
Given that, $\ ^{n}C_{6} = \ ^{n}C_{12}\ \Rightarrow \ \ ^{n}C_{n - 6} = \ ^{n}C_{12}\$
$\Rightarrow \ n - 6 = 12\ \Rightarrow \ n = 18$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.