Answer:
The equation of the parabola is;
x = -(1/4)·(y - 4)² + 3
Step-by-step explanation:
The given focus of the parabola is f = (2, 4)
The directrix of the parabola is x = 4
The vertex form of the equation of the parabola can be expressed as follows;
x = a·(y - k)² + h
(y - k)² = 4·p·(x - h)
Where;
(h, k) = The vertex of the parabola
(h + p, k) = The focus of the parabola
x = h - p = The directrix
Therefore, k = 4
h + p = 2...(1)
h - p = 4...(2)
∴ 2·h = 6
h = 6/2 = 3
From equation (1), we have;
p = 2 - 3 = -1
p = -1
From the equation of the parabola in the form, (y - k)² = 4·p·(x - h), we have;
The equation of the parabola is (y - 4)² = 4 × (-1) ·(x - 3)
Therefore, we have;
(y - 4)² = -4·x + 12
4·x = 12 - (y - 4)²
The equation of the parabola is x = -(1/4)·(y - 4)² + 3
y² -8·y + 16 = -4·x + 12
4·x = 8·y - y² - 16 + 12 = 8·y - y² - 4
x = 2·y - y²/4 - 1 = -y²/4 + 2·y - 1
The equation of the parabola can also be written in the form
x = -y²/4 + 2·y - 1 = -0.25·y² + 2·y - 1
