问题
选择题
已知函数f（x）=x2n+ax的导数f′（x）=2x+3，则数列{
|
答案
∵函数f（x）=x2n+ax的导数f′（x）=2x+3，
∴n=1，a=3
∴函数f（x）=x2+3x
∴
| 1 |
| f(n)+2 |
| 1 |
| n2+3n+2 |
| 1 |
| n+1 |
| 1 |
| n+2 |
∴数列{
| 1 |
| f(n)+2 |
| 1 |
| 2 |
| 1 |
| 3 |
| 1 |
| 3 |
| 1 |
| 4 |
| 1 |
| n+1 |
| 1 |
| n+2 |
| 1 |
| 2 |
| 1 |
| n+2 |
| n |
| 2(n+2) |
故选C．
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