设向量OA=（2,5）,向量OB=(3,1),向量OC=（6,3）,O为坐标原点.

let M be (x,y)
M is on OC
x/y = 6/3
x=2y
M(2y,y)
MA.MB=0
(2-2y,5-y)(3-2y,1-y)=0
(2-2y)(3-2y)+(5-y)(1-y)=0
6-10y+4y^2+5-6y+y^2=0
5y^2-16y+11=0
(5y-11)(y-1)=0
y=11/5 or 1
M( 22/5,11/5) or (2,1)