Lol I seem to be stuck with a lot of questions to do with the parabola.

Q: Show that the normals at P (at^2, 2at) and Q (as^2,2as)on the parabola with equation y^2=4ax meet at the point R where the coordinates of R are

[a(t^2+ts+s^2+2)], -ats(t+s)]. This part of the question I've managed to do. It's the next part that I'm stuck on: Given that the line PQ passes through the focus S(a, 0), show that as t and s vary, R lies on the curve with equation y^2=a(x-3a).

I tried to eliminate the variables t and s, but was unsuccessful. Can someone help please?

Btw, can someone let me know what topic this post should come under for future reference?