Permutations And Combinations Question 157
Question: If $ ^{n}C _{r} $ denotes the number of combinations of n things taken r at a time, then the expression $ ^{n}{C _{r+1}}+{{}^{n}}{C _{r-1}}+2\times {{}^{n}}C _{r} $ equals [AIEEE 2003]
Options:
A) $ ^{n+2}C _{r} $
B) $ ^{n+2}{C _{r+1}} $
C) $ ^{n+1}C _{r} $
D) $ ^{n+1}{C _{r+1}} $
Correct Answer: B
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Answer:
Solution:
BETA
