The length of the chord of the parabola y2=4axwhose equation is.y−x2+4a2=0 is

Any point on the parabola is at2,2at;2at−at22+4a2=0⇒ 2t2−2t−42=0⇒ t1+t2=2,t1t2=−4⇒t1−t2=18at12−at222+2at1−2at22=a182+4=63a.