There is one more method to do this question.
that is by using the equation of the chord whose mid pt. is given S1=T
let the mid pt be (a,0)
Therefore we get a2-ap=ax -px/2 -ap/2 - qy/2
now since pt. (p,q) lies on chord we can satisfy the equation with it
a2-ap-ap+p2/2+ap/2+q2/2=0
2a2-4ap+p2+ap+q2=0
2a2-3ap+(p2+q2)=0
Now,this quadratic shud have two distinct roots as two distinct are bisected by x-axis,hance the discriminant D>0
9p2-8(p2+q2)>0
thus we get p2>8q2
Plz rate if the soln. was helpful.