The following was confusing me so any help would be greatly appreciated!

P(N_i = n_i, i = 1,....,k) = n!/(n_1!n_2!...n_k!) * ((p_1)^(n_1))((p_2)^(n_2))....((p_k)^(n_k)) is known as the multinomial distribution.

Find the marginal distributions of the multinomial distribution.