
Straightline equations are those that are first degree in both x and y. Slope: the measure of “steepness” of a line. Two points on the line are needed to determine the slope. where (x_{1}, y_{1}) and (x_{2}, y_{2}) are the coordinates of any two points on the line Line Equations:
* Equations must be in the slopeintercept form (solved for y ) in order to easily “see” what the slope and y intercept are. Parallel Lines… have the same slopes and different yintercepts Perpendicular Lines… have slopes that are negative reciprocals. If the slope of one line is 4 , then the slope of the perpendicular line is . Graphing Linear Equations:
Vertical Lines… are missing the y variable. The slope of a vertical line is undefined. x = 3 is the equation of a vertical line, where the x coordinate is always 3, and the y coordinate can be any value. Horizontal Lines… are missing the x variable. The slope of a horizontal line is zero. y = 2 is the equation of a horizontal line, where the y coordinate is always 2, and the x coordinate can be any value. Horizontal and Vertical lines are perpendicular. 