| (n+6)(n+5) | 1 | ||
< | |||
| (n+10)(n+9) | 2 |
| (n + 6)(n + 5) | 1 | ||
< | |||
| (n + 10)(n + 9) | 2 |
| 2(n + 6)(n + 5) | (n + 10)(n + 9) | ||
< | |||
| 2(n + 10)(n + 9) | 2(n + 10)(n + 9) |
| 2(n2 + 5n + 6n + 30) − (n2 + 9n + 10n + 90) | |
< 0 | |
| 2(n + 10)(n + 9) |
| 2n2 + 10n + 12n + 60 − n2 − 19n − 90 | |
< 0 | |
| 2(n + 10)(n + 9) |
| n2 + 3n − 30 | |
< 0 | |
| 2(n + 10)(n + 9) |