help with precal problems plz

Can someone please help me figure out what I did wrong with these problems?

1. complete the square to write the equation of the parabola f(x) = -8x^2 - 24x + 15 in (h,k) form.

I can up with:

-8(x-3/2)^2 -3

( 3/2 , -3) ... but this is wrong... I dunno why...

2. find the domain of f(g(x))

f(x) = 1/(x-2) g(x) = 1/(radical x-3)

I came up with:

1/{[1/(radical x-3)] -2 } as the equation and so i know that x ≥ -3 and i also set up the equation (radical x-3) ≠ 1/2 because 1/(1/2) is 2 and 2-2 is 0.

so... how would I write the domain in the (x:x) = (-infinity, a number)(a number, infinity) form?

3. find a relationship between x and y so that (x,y) is equidistant from two points (5,2) and (-1,7). solve for a simplified relationship between x and y, don't solve for x and y.

I had no idea how to solve this one.

Thanks for viewing my thread.