已知点M(-6,7)和点N（-3,y）间的距离是5,则y=___
问题描述：
已知点M(-6,7)和点N（-3,y）间的距离是5,则y=___
答
√{[(-6-(-3)]^2+(7-y)^2}=5
√{(-3)^2+(7-y)^2}=5
√{9+(7-y)^2}=5
9+(7-y)^2=25
(7-y)^2=16
(7-y)^2-16=0
(7-y+4)(7-y-4)=0
(11-y)(3-y)=0
y=11或y=3