The slope-intercept form of a line is $\displaystyle{y}={m}{x}+{b}\usepackage{cmbright}\Huge\$ , where m is equal to the slope of the line and b is equal to the y-intercept. You may not have noticed that the point that the line passes through on the y-axis is $\displaystyle{\left({0},-{2}\right)}\usepackage{cmbright}\Huge\$ , so the y-intercept is negative, not positive.