Question:
Evaluate:
${ }^{n+1} C_{n}$
Solution:
We know that:
${ }^{\mathrm{n}} \mathrm{C}_{\mathrm{r}}=\frac{n !}{(n-r) ! \times r !}$
$\Rightarrow^{n+1} \mathrm{Cn}=\frac{(n+1) !}{(n+1-n) ! \times n !}$
$\Rightarrow^{n+1} C_{n}=\frac{(n+1) !}{1 ! \times n !}$
$\Rightarrow^{n+1} C_{n}=\frac{(n+1) !}{1 \times n !} \ldots(1 !=1)$
$\Rightarrow^{n+1} C_{n}=\frac{(n+1) \times n !}{1 \times n !}$
$\Rightarrow{ }^{n+1} C_{n}=\frac{(n+1)}{1}$
$\Rightarrow^{n+1} C_{n}=n+1$
Ans: ${ }^{n+1} C_{n}=n+1$