First slide

Binomial theorem for positive integral Index

Question

$If the coefficients of x^{9}, x^{10}, x^{11} in the expansion of (1 + x)^{n} are in arithmetic$ $progression then n^{2} - 41 n =$

Moderate

A

398
B

298
C

-398
D

198

Solution

$\begin{array}{l} Coefficients of x^{9}, x^{10}, x^{11} in (1 + x)^{n} are in A.P \Rightarrow n^{2} - 41 n + 400 = 2 \\ \Rightarrow n^{2} - 4 \ln + 398 = 0 \Rightarrow n^{2} - 41 n = - 398 . \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App