Above the x-axis: When a function is above the x-axis, it means that its y-values are positive or greater than zero on that interval.
Zero-crossing: A zero-crossing refers to points where a function intersects or crosses over the x-axis. At these points, y-values change sign from positive to negative or vice versa.
Sign chart: A sign chart helps analyze changes in sign (positive or negative) of an expression or equation within different intervals by examining factors affecting its value.