1 |
4 |
1 |
3 |
故方程ax2-bx+1=0的两根是x1=
1 |
4 |
1 |
3 |
所以
1 |
a |
1 |
12 |
b |
a |
7 |
12 |
所以a=12,b=7.
(2)∵b=a+2,
∴f(x)=ax2-(a+2)x+1=a(x-
a+2 |
2a |
(a+2)2 |
4a |
对称轴x=
a+2 |
2a |
1 |
2 |
1 |
a |
当a≥2时,x=
a+2 |
2a |
1 |
2 |
1 |
a |
1 |
2 |
∴f(x)min=f(
a+2 |
2a |
(a+2)2 |
4a |
当a=1时,x=
a+2 |
2a |
1 |
2 |
1 |
a |
3 |
2 |
综上可得:a=1或a=2.
1 |
4 |
1 |
3 |
1 |
4 |
1 |
3 |
1 |
4 |
1 |
3 |
1 |
a |
1 |
12 |
b |
a |
7 |
12 |
a+2 |
2a |
(a+2)2 |
4a |
a+2 |
2a |
1 |
2 |
1 |
a |
a+2 |
2a |
1 |
2 |
1 |
a |
1 |
2 |
a+2 |
2a |
(a+2)2 |
4a |
a+2 |
2a |
1 |
2 |
1 |
a |
3 |
2 |