It was a tricky little thing...I think i got it out but i fudged it towards the end:
x = (1/p)(p^2-1/p^2)
y = (p)(1/p^2-p^2)
= (-p)((p^2-1/p^2)
Then x/y = (1/p)/(-p) = -1/p^2
So y/x = -p^2
Its pretty simple from here on, every where you see p^2 sub that in, and everywhere you see p sub...