1.10 – Lines
Video 1 of 3: Formulas for Line Components
Video 2 of 3: General Equations for Lines
Video 3 of 3: Parallel and Perpendicular Lines
Section Notes
Point-Slope Form of the Equation of a Line
An equation of the line that passes through the point and has slope
is
Slope-Intercept Form of the Equation of a Line
An equation of the line that has slope and
intercept
is
Vertical and Horizontal Lines
An equation of the vertical line through is
.
An equation of the horizontal line through is
.
General Equation of a Line
The linear equation
is the general form of a line
Parallel Lines
Two (nonvertical) lines are parallel if and only if they have the same slope
Perpendicular Lines
Two lines with slopes and
are perpendicular if and only if
, that is, the slopes are negative reciprocals of each other:
Furthermore, a horizontal line (with slope 0) is perpendicular to a vertical line (undefined slope)