Apparently your equation is:

x = 2/[(y-3)^2 - 1]

because that's the only thing that makes sense with what you are saying.

Look at just the denominator:

(y - 3)^2 - 1

I'm going to multiply out the (y - 3)^2:

(y - 3)^2 = (y - 3)(y - 3) = y(y - 3) - 3(y - 3) = y^2 - 3y - 3y + 9 = y^2 - 6y + 9

So

(y - 3)^2 - 1 = y^2 - 6y + 9 - 1 = y^2 - 6y + 8

as advertised.

-Dan