坐標（兩點之間距離）Distance between poins

X(-1,2)
Y(-1,y)
Z(z,-2)

XY=3
[(-1)-(-1)]^2+[(-2)-(y)]^2=3^2 (pyth. thm)
-2-y=3 or -2-y=-3
y=-5 or 1

XZ=5
[(-1)-(y)]^2+[(-2)-(-2)]^2=5^2 (pyth. thm)
-1-y=-5 or -1-y=5
y=4 or -6

2007-07-18 16:05:47 補充：
XZ=5[(-1)-(y)]^2+[(-2)-(-2)]^2=5^2 (pyth. thm)-1-y=-5 or -1-y=5y=4 or -6 個y轉做z

不知道................................................