Given, equation of parabola y2=16x LL′=4a=16 End points of latusrectum is (a1±2a) Coordinates of L is (4,8) and L′ is (4,−8). The end points of focal length is The end points of focal length is (at2,2at)‌ and ‌(‌a∕t2,−‌2a∕t) Coordinate of P is (1,4) ⇒at2=1,‌2at=4 ⇒4t2=1,‌2×4×t=4 ⇒‌‌t2=‌