﹙1﹚x²-3x-6=0.
x1·x2=﹣6
x²-6x+3=0
x1′·x2′=3
∴ x1·x2·x1′·x2′=﹙﹣6﹚×3=﹣18.
﹙2﹚ x1+x2=﹣b/a=﹣4
b=4a
x1·x2=c/a=3
c=3a
x=﹣b/2a=﹣4a/2a=﹣2
y=c-b²/4a=3a-16a²/4a=﹣a
∴ 顶点坐标为:﹙﹣2,﹣a﹚.
﹙1﹚x²-3x-6=0.
x1·x2=﹣6
x²-6x+3=0
x1′·x2′=3
∴ x1·x2·x1′·x2′=﹙﹣6﹚×3=﹣18.
﹙2﹚ x1+x2=﹣b/a=﹣4
b=4a
x1·x2=c/a=3
c=3a
x=﹣b/2a=﹣4a/2a=﹣2
y=c-b²/4a=3a-16a²/4a=﹣a
∴ 顶点坐标为:﹙﹣2,﹣a﹚.