题干
设 f(x)=
，曲线y=f（x）在点（1，f（1））处的切线与直线x+y+1=0垂直．
| ( |
| 4 |
| x |
| + |
| a |
| ) |
| l |
| n |
| x |
| 3 |
| x |
| + |
| 1 |
