设点A(-2,-5)关于直线L:X-2Y+2=0对称点A'(X',Y'),
AA'垂直L,斜率之积=-1,AA'中点在L上,
(1/2)[(Y'+5)/(X'+2)]=-1
[(-2+X')/2]-2[(-5+Y')/2]+2=0
解得X'=-6,Y'=3
A(-2,-5)关于直线L:X-2Y+2=0对称点为(-6,3).