设c点的坐标是x₁,d点的坐标是₂
(1) c - (-4) = c + 4 = 5, c = 1
(2) |BD|² = 36, |d - (-2)|² = 36
(d + 2)² = 36, d² + 4d - 32 = 0
(d + 8)(d - 4) = 0
d₁= 4 （舍去,因为与A点坐标相同）
d₂= -8
(3) ∵向量AC = -3向量AD
∴c + 4 = -3(d + 4)
∴d - (c + 4) = d + 3(d + 4)
d - c = 4d + 16
3(d - c) = 12(d + 4)
∴3CD = 12(d + 4)
这部分题目有误.