题目内容
| lim |
| n→∞ |
| ||
|
| A．0 | B．2 | C．
| D．
|
∵
=
，
=
，
∴
=
×
=
=
．
∴
=
=
．
故选D．
| C | n2n |
| (2n)! |
| n!(2n-n)! |
| C | n+12n+2 |
| (2n+2)! |
| (n+1)!(n+1)! |
∴
| ||
|
| (2n)! |
| n!n1 |
| (n+1)!(n+1)! |
| (2n+2)! |
| (n+1)(n+1) |
| (2n+2)(2n+1) |
| n2+2n+1 |
| 4n2+6n+2 |
∴
| lim |
| n→∞ |
| ||
|
| lim |
| n→∞ |
| n2+2n+1 |
| 4n2+6n+2 |
| 1 |
| 4 |
故选D．
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