设过点P的直线方程为y=k(x-4)k=0时,直线平行于y轴.x=4代入抛物线方程,解得y1=4,y2=-4y1^2+y2^2=32k≠0时,x=y/k+4,代入抛物线方程：y^2=4(y/k+4)整理,得ky^2-4y-16k=0由韦达定理得y1+y2=4/k y1y2=-16y1^2+y2^2=(y1+y2...