Which is the standard form of the equation of the parabola that has a vertex of (–4, –6) and a directrix of y = 3?

Hello,

focus=(-4,-15)

If focus =(a,b) and directrix y=k
the parabola is:
y=1/(2(b-k)) * (x-a)²+(b+k)/2

So y=1/(2*(-15-3))*(x+4)²+(-15+3)/2
y=-(x+4)²/36 -6