慢四步
幼苗
共回答了25个问题采纳率:96% 举报
x² + y² - 4x + 2y + m = 0
(x - 2)² + (y + 1)² = 5 - m
圆心为P(2, -1); 设半径r, r² = 5 - m
从P向y轴做垂线,垂足C(0, -1)
不妨设A在B上方, 取a > 0, 则A(0, -1 + a), B(0, -1 - a)
AP⊥PB
AB² = AP² + BP²
(-1 + a + 1 + a)² = r² + r² = 2(5 - m)
a² = (5 - m)/2
A在圆上: (0 - 2)² + (-1 + a + 1)² = 5 - m
a² + 4 = 5 - m
(5 - m)/2 + 4 = 5 - m
m = -3
1年前
5