defence exam Agniveer Vayu Group X & XY Mock Test 01/2026 Mathematics Permutations and Combinations Combination Function and its properties
\(\rm ^nC_{r-3}+2\times (^nC_{r-4})+{^nC_{r-5}}=\)
1
\(\rm ^{(n+2)}C_{r- 4}\)
2
\(\rm ^{(n+2)}C_{r- 5}\)
3
\(\rm ^{(n+1)}C_{r- 3}\)
4
\(\rm ^{(n+2)}C_{r- 3}\)