(西南师大附中高2009级第三次月考)已知圆C经过P.Q两点.且在y轴上截得的线段长为.半径小于5． (1)求直线PQ与圆C的方程． (2)若直线l∥PQ.且l与圆C交于点A.B..求直线l的方程——青夏教育精英家教网—

(西南师大附中高2009级第三次月考)已知圆C经过P.Q两点.且在y轴上截得的线段长为.半径小于5． (1)求直线PQ与圆C的方程． (2)若直线l∥PQ.且l与圆C交于点A.B..求直线l的方程．解:(1) PQ为···························································· 2分 C在PQ的中垂线即y = x – 1上································ 3分设C(n.n – 1).则······································· 4分由题意.有······································································· 5分 ∴ ∴ n = 1或5.r 2 = 13或37(舍)······················ 7分 ∴圆C为············································································· 8分解法二: 设所求圆的方程为由已知得解得当时.,当时.(舍) ∴ 所求圆的方程为 (2) 设l为···················································································· 9分由.得································ 10分设A(x1.y1).B(x2.y2).则················ 11分 ∵ . ∴ ···················································· 12分 ∴ ∴ ∴ m = 3或 – 4(均满足) ∴ l为···························································· 14分【查看更多】

题目列表(包括答案和解析)

（08年东北师大附中文）（12分）

已知等差数列，，公差，且，，成等比数列，．