| (n+2)!+(n+1)! | ||
an= | ||
| (n+3)! |
| (n+2)!+(n+1)! | ||
an= | ||
| (n+2)!−(n−1)! |
| (n+1)!(n+2+1) | n+3 | 1 | ||||
an= | = | = | →0 | |||
| (n+1)!(n+2)(n+3) | (n+2)(n+3) | n+2 |
| (n−1)![n(n+1)(n+2)+n(n+1)] | ||
an= | = | |
| (n−1)![n(n+1)(n+2)−1] |
| n(n2+3n+2)+n2+n | n3+4n2+3n | |||
= | = | = | ||
| n(n2+3n+2)−1 | n3+3n2+2n−1 |
| 1+4n+3n2 | 1+0+0 | |||
= | → | =1 | ||
| 1+3n+2n2−1n3 | 1+0+0−0 |