Question

fatorial 2n!-(2n+1)!/2n!

Answer 1

2n! - (2n+1)!/2n!
2n! - (2n+1)2n!/2n!
colocando o fator comum em evidência 
2n![1-(2n+1)]/2n!
1-(2n+1)
1-2n-1
-2n