y^2=4x
焦点F(1,0),准线x=-1
倾斜角为60度,则斜率=√3
直线L的方程
y=√3(x-1)
代入y^2=4x
3x^2-10x+1=0
x1+x2=10/3
|AB|=|FA|+|FB|=x1+1+x2+1
=x1+x2+2
=16/3