(1)设抛物线与x轴交点的横坐标为x1,x2,
∴关于x的方程2x2-3x+m=0,
△=(-3)2-8m=9-8m>0得m<
9 |
8 |
∵x1+x2=
3 |
2 |
m |
2 |
∴AB=|x1-x2|=
(x1+x2)2−4x1x2 |
| ||
2 |
又∵AB=
1 |
2 |
∴
| ||
2 |
1 |
2 |
∴m=1;
(2)∵m=1,
∴抛物线为y=2x2-3x+1,
其顶点P的纵坐标为yP=
4ac−b2 |
4a |
1 |
8 |
∴S△ABP=
1 |
2 |
=
1 |
2 |
1 |
2 |
1 |
8 |
1 |
32 |
1 |
2 |
9 |
8 |
3 |
2 |
m |
2 |
(x1+x2)2−4x1x2 |
| ||
2 |
1 |
2 |
| ||
2 |
1 |
2 |
4ac−b2 |
4a |
1 |
8 |
1 |
2 |
1 |
2 |
1 |
2 |
1 |
8 |
1 |
32 |