Answer:
b
Explanation:
A parabola represents a quadratic equation. For a point called the focus and a line called the directrix, the distance from each point of the parabola to the focus is equal to its distance to the directrix. For example, if the directrix of the parabola was y=0 and the focus was (1,1), the distance between each point on the parabola to (1,1) would be equal to its distance from the line y=0.
For a parabola that has a horizontal axis of symmetry (or when y² is in the equation rather than x²), one way to write its equation is of the form
(y-k)² =4p(x-h), where (h,k) is the vertex. Now, we can try to match up this form with the equation we have,
y² = 24x
(y-k)² = 4p(x-h)
We can start by setting both sides with y equal to each other, as well as both sides containing x
y² = (y-k)²
square root both sides
y = y-k
k=0
24x = 4p(x-h)
divide both sides by 4
6x = p(x-h)
expand
6x = p*x - p*h
Because p*h does not contain an x value, we can say
6x = p * x
p = 6
6x = p*x - p*h
6x = 6x-6*h
subtract 6x from both sidex
6*h=0
h=0
Our equation is thus
y= 4(6)(x), with our vertex being (0,0) = (h,k)
The directrix is equal to x=h-p, and with p being 6, our directrix is thus
x=0-6 = -6
x=-6