Line [math]a[/math] and Line [math]b[/math] are perpendicular lines. Their slopes are negative reciprocals. Move line [math]a[/math]. Line [math]a[/math] stays perpendicular to line [math]b[/math]. [math]y=mx+b[/math] is the slope-intercept form of a linear equation. The slope is [math]m[/math].