At the state fair, Erin and her cousin ride the Ultra Drop roller coaster. When the ride plummets down the first hill, it dips below the loading platform. At the bottom, a camera snaps the riders' picture before hurtling them back toward the sky. The equation
y = x2 -9x +20 models the roller coaster's path over time. The variable y represents height (in feet) above or below the platform. At y = 0, the roller coaster is even with the platform. The variable x represents the amount of time (in seconds) since the ride began.
Factor the equation to better understand Erin's ride.