Question 50606
18. x^2 + 4x - 28y + 88 = 0 
Rewrite as follows:
x^2+4x+? = 28y-88+?
Complete the square to get:
x^2+4x+4 = 28y-88+4
(x+2)^2 = 4(7)(y-(11/7))
This follows the form (x-h)^2=4p(y-k)
where (h,k) is the vertex.
Vertex at (-2,11/7)

Follow the same procedure for #'s 19 and 20.
19. x^2 - 2x + 44y + 353 = 0 
20. x^2 + 6x + 8y + 25 = 0 

Cheers,
Stan H.