The linear function in slope-intercept form: y = ax + b. a - slope. Monotonicity: a * 0 - strictly increasing, a * 0 - strictly decreasing, a = 0 - constant. b - intercept, the y-value of the point where it crosses the y-axis (0,b). The graph of linear function: y = 2x + 3 (slope a = 2, monotonicity: strictly increasing, point where it crosses the y-axis: (0,3)). y = -1/3x + 1 (slope a = -1/3, monotonicity: strictly decreasing, point where it crosses the y-axis: (0,1)). y = 2 (slope: a = 0, monotonicity: constant, point where it crosses the y-axis: (0,2)). Angle of a line with x-axis.