For (2 leq r leq n,binom{n}{r} + 2binom{n}{r - 1} + binom{n}{r - 2} =): Permutations and Combinations (Mathematics) Question | DivineJEE

For (2 leq r leq n,binom{n}{r} + 2binom{n}{r - 1} + binom{n}{r - 2} =): Permutations and Combinations (Mathematics) Question | DivineJEE | divineJEE