When graphed, which parabola opens downward? y = –3x2 y = (x – 3)2 y = x2 – 3

we know that

the equation of a vertical parabola into vertex form is equal to

where

(h,k)-------> is the vertex of the parabola

if -------> the parabola open upwards

if -------> the parabola open downwards

case A)

so

-------> the parabola open downwards

the vertex is the point ------> is a maximum

therefore

open downwards

case B)

so

-------> the parabola open upwards

the vertex is the point --------> is a minimum

therefore

open upwards

case C)

so

-------> the parabola open upwards

the vertex is the point --------> is a minimum

therefore

open upwards

therefore

the answer is

open downwards