The equations that, when graphed, will form a parabola are those that can be expressed in the form of \( y = ax^2 + bx + c \), where \( a \) is not equal to zero.
From your list, the equations that are parabolas are:
- \( y = 6x^2 \) (which is a quadratic equation with \( a = 6 \))
- \( y = -4x^2 \) (which is a quadratic equation with \( a = -4 \))
The other equations do not represent parabolas:
- \( y = 2^x \) is an exponential function.
- \( y = 16x + 6 \) is a linear equation.
- \( y = (-9)^x \) is an exponential function.
- \( y = 8x \) is a linear equation.
So, the correct responses are:
- \( y = 6x^2 \)
- \( y = -4x^2 \)