For \[2\le r\le n,\left( \begin{matrix} n \\ r \\ \end{matrix} \right)+2\,\left( \begin{align} & \,\,n \\ & r-1 \\ \end{align} \right)\]\[+\left( \begin{matrix} n \\ r-2 \\ \end{matrix} \right)\] is equal to [IIT Screening 2000; Pb. CET 2000]

\[\left( \begin{matrix} n+1 \\ r-1 \\ \end{matrix} \right)\]

\[2\,\left( \begin{matrix} n+1 \\ r+1 \\ \end{matrix} \right)\]

\[2\,\left( \begin{matrix} n+2 \\ r \\ \end{matrix} \right)\]

\[\left( \begin{matrix} n+2 \\ r \\ \end{matrix} \right)\]

For \[2\le r\le n,\left( \begin{matrix} n \\ r \\ \end{m

1.	For \[2\le r\le n,\left( \begin{matrix} n \\ r \\ \end{matrix} \right)+2\,\left( \begin{align} & \,\,n \\ & r-1 \\ \end{align} \right)\]\[+\left( \begin{matrix} n \\ r-2 \\ \end{matrix} \right)\] is equal to [IIT Screening 2000; Pb. CET 2000]
A.	\[\left( \begin{matrix} n+1 \\ r-1 \\ \end{matrix} \right)\]
B.	\[2\,\left( \begin{matrix} n+1 \\ r+1 \\ \end{matrix} \right)\]
C.	\[2\,\left( \begin{matrix} n+2 \\ r \\ \end{matrix} \right)\]
D.	\[\left( \begin{matrix} n+2 \\ r \\ \end{matrix} \right)\]
Answer» E.

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For \[2\le r\le n,\left( \begin{matrix} n \\ r \\ \end{matrix} \right)+2\,\left( \begin{align} & \,\,n \\ & r-1 \\ \end{align} \right)\]\[+\left( \begin{matrix} n \\ r-2 \\ \end{matrix} \right)\] is equal to [IIT Screening 2000; Pb. CET 2000]

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