x² - 16x + y + 68 = 0
---> y = -x² + 16x - 68
Complete the square:
---> y + 68 = -x² + 16 x
Factor out the negative sign:
---> y + 68 = -(x² - 16 x)
Complete the square by dividing the linear term by 2, squaring the rsult and adding that result to both sides:
---> y + 68 - 64 = -(x² - 16x + 64)
---> y + 4 = -(x - 8)²
The vertex is: (8, -4)
The focal length is found using: f = 1/(4a) ---> f = 1/(4·-1) = -1/4
The focal point will be at (8, -4 - 1/4) = (8, -4 1/4)
The directrix will be: y = -4 + 1/4 ---> y = -3 1/4