zdhqf
幼苗
共回答了15个问题采纳率:100% 举报
圆心在AB的中垂线上, x + 2y = 0为AB的中垂线, x + 2y = 0和4x + 5y = 9的交点为圆心C(6, -3)
![](https://img.yulucn.com/upload/6/3d/63dbcef9b6fd6f42733fbbe3661546f1_thumb.jpg)
半径r, r² = CA² = (6 - 2)² + (-3 - 3)² = 52
圆的方程: (x - 6)² + (y + 3)² = 52
x + 2y = 0,y = -x/2,斜率-1/2
AB斜率2, 方程y - 3 = 2(x - 2), y = 2x - 1
与x + 2y = 0交于D(2/5, -1/5)
D为AB的中点, B(x, y)
(2 + x)/2 = 2/5, x = -6/5
(3 + y)/2 = -1/5, y = -17/5
B(-6/5, -17/5)
1年前
9