Permutation and CombinationHard
Question
If nCr denotes the number of combinations of n things taken r at a time, then the expression nCr + 1 + nCr-1 + 2 × nCr equals
Options
A.n+2Cr
B.n+2Cr+1
C.n+1Cr
D.n+1Cr+1
Solution
nCr+1 + nCr-1 + nCr + nCr
= n+1Cr+1 + n+1Cr
= n+2Cr+1.
Hence, (B) is the correct answer
= n+1Cr+1 + n+1Cr
= n+2Cr+1.
Hence, (B) is the correct answer
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