Class 11

Math

JEE Main Questions

Permutations and Combinations

The number of ways of choosing triplet $(x,y,z)$ such that $z>max{x,y}$ and $x,y,z∈{1,2,……….n,n+1}$ is $(A)$ $._{n}+1C_{3}+_{n+2}C_{3}$
$(B)$$n(n+1)(2n+1)/6$ $(C)$$1_{2}+2_{2}+…………..+n_{2}$
$(D)$ $2(._{n+2}C_{3})−(._{n+1}C_{2})$