Answer:
D. 21 ft
Step-by-step explanation:
We need to use Power of Points, which basically says that for intersecting chords in a circle (see attachment), a * b = c * d.
Here, we can say that a = x, b = 6, c = 7, and d = 18. Then, we have the equation:
ab = cd
x * 6 = 7 * 18
6x = 126
x = 21
Thus, x is 21 ft.
Hope this helps!
Answer:
Step-by-step explanation:
∵ The quadratic equation form is :
y = [1/2(b - k)] (x - a)² + (b + k)/2
Where (a , b) is the focus and directrix y = k
∵ The focus is (4 , -3) and directix is y = -6
∵
∴
∴
another way:
Assume that (x , y) is the general point on the parabola
∵ The distance between the directrix and (x , y) = the distance between the focus and (x , y)
By using the distance rule:
∵ (y - -6)² = (x - 4)² + (y - -3)² ⇒ (y + 6)² = (x - 4)² + (y + 3)
∴ y² + 12y + 36 = (x - 4)² + y² + 6y + 9
∴ 12y - 6y = (x - 4)² + 9 - 36
∴ 6y = (x - 4)² - 27 ⇒ ÷ 6
∴ y = 1/6 (x - 4)² - 9/2