Let `A={1,2,..., n}` and `B={a , b` }. Then number of subjections from `A` into `B` is nP2 (b) `2^n-2` (c) `2^n-1` (d) nC2

Explanation

As, the number of surjections from `A` to `B` is equal to the number of functions from `A` to `B` minus the number of functions from `A` to `B` whose images are proper subsets of `B`.
And, the number of functions from a set with `n` number of elements into a set with `m` number of elements `=m^n`
So, the number of surjections from `A` into `B` where,
`A={1,2,....,n} `and `B={a,b}` is
`2^n-2`(As, two functions can be many-one into functions )