设方程为x^2=2py联立X-2Y-1 =0x^2－px+p=0.设交点坐标为（x1,y1）(x2,y2).x1+x2=p,x1x2=p,√[1+k^2]×|x1-x2|=√[1+(1/2)^2]×√[(x1+x2)^2-4x1x2]=√15,解得p=-2或p=6,故方程为x^2=-4y或x^2=12y...