(1) x = 6,y = 6/3 + b = 2 + b = 0,b = -2
y = x/3 - 2
B(0,-2)
C(0,c),c > 0
BC = c -(-2) = c + 2 = 5,c = 3
C(0,3)
(2)图自己画,有两种可能：
(a) AD//BC,CD = AB
AB² = (-2)² + 6² = 40
D(6,d)
CD² = (0 - 6)² + (3 - d)² = 36 + (3 - d)² = 40
d = 1 (舍去d = 5,此时ABCD为平行四边形)
D(6,1)
(b) CD//BA,BC = AD
BC² = 25
CD的方程:y = x/3 + 3
D(d,d/3 + 3)
AD² = (d - 6)² + (d/3+ 3- 0)² = 25
d² - 9d + 18 = (d - 3)(d - 6) = 0
d = 3 (舍去d = 6,此时ABCD为平行四边形)
D(3,4)