Given, y2=16x a‌=4 P(4,8)‌≡(at12,2at1) 2at1‌=8 8t1‌=8,⇒t1=1 If PQ is a focal chord, then ‌t1t2=−1⇒+1×t2=−1 ‌t2=−1 ‌Q(at22,2at2)≡Q(4,−8) ‌R(16,16)≡(at32,2at3) ‌2at3=16 ‌8t3=16⇒t3=2 If RT is a focal chord, then t3t4=−1 ‌2×t4=−1⇒t4=‌