(1)由两点式写方程得 y?5 ?1?5 = x+1 ?2+1 ,即6x-y+11=03或直线AB的斜率为k= ?1?5 ?2?(?1) = ?6 ?1 =6直线AB的方程为y-5=6(x+1)即6x-y+11=0(2)设M的坐标为(x0,y0),则由中点坐标公式得x0= ?2+4 2 =1,y0= ?1+3 2 =1故M(1,1)AM= (1+1)2+(1?5)2 =2 5