If (x1,y1) and (x2,y2) are the extremities of a focal chord of the parabola 3y2=4x, then x1x2+y1y2 is equal to −pq where p,q are co-prime. Then value of q−p is
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Solution
If (at21,2at1),(at22,2at2) are the ends of a focal chord of a parabola y2=4ax, then t1t2=−1
Here, x1=at21=13t21,x2=13t22 y1=23t1,y2=23t2 ∴x1x2+y1y2 =19(t1t2)2+49t1t2=19−49=−13=−pq∴q−p=2