设直线的斜率为k(k≠0),则方程为：y+1=k(x-2),代入抛物线方程,得：[k(x-2)-1]^2-4x=0,或y^2=4(y+1+2k)/k,整理得：k^2x^2-(4k^2+2k+4)x+(2k+1)^2=0,或ky^2-4y-4(2k+1)=0,设A为(x1,y1),B为(x2,y2),则：x1*x2=(2k+1)^2/...