Find the value of y when x equals negative 15 negative -x - 9y equals 39​

answer is

b.

11

hope you get this one right.

the equation of the parabola is y2=12x

explanation:

the vertex is midway between the focus ad the directrix

so, the vertex is (0,0)

let p=(x,y) be a point on the parabola.

the distance of p from the directrix is equal to the distance from the focus.

x+3=√(x−3)2+(y−0)2

(x+3)2=(x−3)2+y2

x2+6x+9=x2−6x+9+y2

y2=12x

graph{y^2=12x [-10, 10, -5, 5]}