Chapter 9 - Solving Quadratic Equations - 9.5 - Solving Quadratic Equations Using the Quadratic Formula - Exercises - Page 524: 74

A - b B - c C - a

When the discriminant is zero, there is one $x$-intercept. So graph $A$ corresponds to $b$. When the discriminant is positive, there are two $x$-intercepts. So graph $C$ corresponds to $a$. When the discriminant is negative, there is no $x$-intercept. So graph $B$ corresponds to $c$.