Identifying Characteristics of Quadratic Functions

For a quadratic function on the form $y=a{x}^2+bx+c$, a positive value of $a$ gives an opening upward and a negative value gives an opening downward.

We see in the figure that the curves with a positive coefficient in front of $x^2$ are $A$ and $D$, while $B$ and $C$ have negative coefficients.

We can read that a curve with an absolute maximum will have a negative coefficient in front of the $x^2$-term. The function that this applies to is $h(x)=9x-6x^2+0.3,$ where $a=\text{-}6$, which then must be the only function with a maximum point.