Chapter 3 - Polynomial and Rational Functions - Exercise Set 3.1 - Page 345: 76

If the coefficient of $x^{2}$ (the value of a in $ax^{2}+bx+c$) is positive, the parabola opens upward. If the coefficient of $x^{2}$ is negative, the parabola opens downward.

If the coefficient of $x^{2}$ (the value of a in $ax^{2}+bx+c$) is positive, the parabola opens upward. If the coefficient of $x^{2}$ is negative, the parabola opens downward.