Got another Q here.
P(2at,at^2) and Q(2as,as^2) are two points on the parabola x^2=4ay . The chord PQ subtends a right angle at the origin. If R is the fourth vertex of the rectangle POQR show that
R parametrically is x=\frac{2at^2-4}{t},y=\frac{a(t^4+16)}{t^2} when st=-4