(1)
A'和A关于y = x对称,则将A的纵横坐标交换即为A'的坐标,即A'(4,1)
A在y = k/x上,k = 1*4; A':4*1 = 4, 满足y = 4/x, 即A'在y = 4/x上
(2)
B在y = x上,则B(m, m)
AA'与y = x垂直,则其斜率为-1, BB的斜率k也是-1
BB': y - m = (-1)(x - m)
y = 2m - x
y = 2m - x = 4/x
x² - 2mx + 4 = 0
按图,较大的根(m + √(m² - 4))为B'的横坐标, B'(m + √(m² - 4), m - √(m² - 4))
A'A² = 18
B'B² = 2(m² - 4)
二者相等,m² - 4 = 9
m = √13