Graphing+Lines


 * Graphing horizontal and vertical lines**

The equation or rule for a horizontal line is y = A, where A is any number since all the points on a horizontal line will have the same y-co-ordinate. e.g. (1, 3), (2, 3), (3, 3), (4, 3), etc. Please note that this a variation of the slope-intercept equation in which the slope is zero.

Graph the following lines: a) y = 3 b) y = 5 c) y = 0 d) y = -4 e) y = -7

The equation or rule for a vertical line is x = B, where B is any number since all the points on a vertical line have the same x-co-ordinate. e.g. (2, -3), (2, -2), (2, -1), (2, -1, (2, 2), etc

Graph the following lines: a) x = -3 b) x = 5 c) y = 0 d) y = 2 e) y = -1,

In order to graph other lines, all one needs is a point and a direction (slope).
 * Graphing other lines**

In **direct variation** (y = mx), all the lines pass through the origin (0, 0). The slope can be used to determine a second point and the relation may be graphed. Note that this is a form of the slope-intercept equation (y = mx + b) in which the y-intercept is zero. In **partial variation** (y = mx +b) the lines will start with the y-intercept (0, b). The slope can be used to determine a second point and the relation may be graphed.

With the **point-slope equation**, the information is read directly from the equation. y = m (x - p) + q, where m is the slope and (p, q) are the co-ordinates of a point on the line.