Question

点(2,5)关于直线x-3y+3=0的对称点的坐标是

Answer 1

设对称点的坐标为P(x,y)点(2,5)与点P(x,y)中点坐标为[(x+2)/2,(5+y)/2]

(y-5)/(x-2)=-3

(x+2)/2-3*(5+y)/2+3=0

解得x=4,y=-1

所以P(4,-1)