In the expansion of $(1+x)^n$ the coefficients of $p$ th and $(p+1)$ th terms are respectively $p$ and $q$,…
In the expansion of $(1+x)^n$ the coefficients of $p$ th and $(p+1)$ th terms are respectively $p$ and $q$, then $p+q$ is equal to
- $n$
- $n+1$
- $n+2$
- $n+3$
Solution
We have,
$
\begin{aligned}
T_p & ={ }^n C_{p-1}=p \\
T_{p+1} & ={ }^n C_p=q \\
\therefore \quad \frac{p}{q} & =\frac{{ }^n C_{p-1}}{{ }^n C_p} \\
\Rightarrow \quad \frac{p}{q} & =\frac{p}{n-p+1} \Rightarrow p+q=n+1
\end{aligned}
$
Asked in: AP EAMCET 2002
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