在平面直角坐标系xOy中,曲线y=x²-6x+1与坐标轴的交点都在圆c上 求圆c的方程?


答:
曲线y=x² -6x+1与y轴的交点: D(0, 1)
y = x² -6x+1 = 0
解得:x = 3±2√2
与x轴的交点: A(3-2√2, 0), B(3+2√2, 0)
曲线y=x² -6x+1为抛物线,对称轴为x = 3
显然圆心C在对称裂桥轴上,设C(3, b)
CA = CD =R
CA² = CD²
(3 - 3 + 2√2)² + (b - 0)² = (3- 0)² + (b - 1)²
8 + b² = 9 + b² - 2b + 1
b = 1
C(3, 1)
C, D的纵坐标相同,距离为横坐燃陵标之差.
R = 3-0 = 3
圆C的皮源戚方程: (x - 3)² + (y - 1)² = 9