(y-3)=k1(x+1) (1)
(y-2)=k2(x-4) (2)
(1)*(2)
(y-3)(y-2)=k1*k2(x+1)(x-4)
因为k1*k2=-1,y=0.
所以得 x^2-3x+2=0
x1=1 x2=2