Resposta :
a) n! / (n-1)
= [n(n - 1)(n -2)!] / (n - 1) = n(n -2)!
b) X! / (X-2)!
= X(X - 1)(X - 2)! / (X - 2)! = X(X + 1)
c) (n+1) / n(n - 1)(n - 2)!
= 1 / n(n - 2)!
d) X!(X+2)! / (X - 1)!.(X + 1)!
= X(X - 1)!.(X +2 )(X + 1)! / ((X - 1)!.(X + 1)! = X(X + 2)
e) (N-1)!+(N-2)! / N
= [(N - 1)(N - 2)! + (N - 2)!] / N = (N - 2)![(N - 1) + 1} / N = (N - 2)!.N / N = (N - 2)!