Distance of a point P on the parabola y2=48x fromthe focus is l and its distance from the tangent atthe vertex is d, then l – d is equal to

Any point on the parabola is P12t2,24t whosedistance from the focus (12, 0) is 12(t2+1=t andfrom y-axis, the tangent at the vertex is 12t2=d.So l – d = 12.