Answer:
y = (-1/19)(x - 8)² + 1521/76
Explanation:
A parabola moves in such a way that it's distance from it's focus and directrix are always equal.
Now, we are given that directrix is y = 9.75 and focus is at (8, 0.25). Focus can be rewritten as (8, ¼) and directrix can be rewritten as y = 39/4
If we consider a point with the coordinates (x, y), it means the distance from this point to the focus is;
√((x - 8)² + (y - ¼)²)
Distance from that point to the directrix is; (y - 39/4)
Thus;
√((x - 8)² + (y - ¼)²) = (y - 39/4)
Taking the square of both sides gives;
((x - 8)² + (y - ¼)²) = (y - 39/4)²
(x - 8)² + y² - ½y + 1/16 = y² - (39/2)y + (39/4)²
Simplifying this gives;
(x - 8)² - (39/4)² = (½ - 39/2)y
(x - 8)² - 1521/4 = -19y
(x - 8)² - 1521/4 = -19y
Divide both sides by -19 to get;
y = (-1/19)(x - 8)² + 1521/76