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JEE MATHEMATICS MCQ: COMBINATIONS

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Application +4 | -1

The expression

{\;^n}{C_r} + 4.{\;^n}{C_{r - 1}} + {6.^n}{C_{r - 2}} + 4.{\;^n}{C_{r - 3}} + {\;^n}{C_{r - 4}}

equals

View answer and explanation

Correct option: A

{\;^{n + 4}}{C_r}

Option A (

{{\;^{n + 4}}{C_r}}

) is correct because the given expression simplifies to this using the identity nCr + nCr-1 = n+1Cr repeatedly.

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n