4.1  Graphing Linear Equations in One Variable

Mrs. Agriesti's Algebra

Goal:  To learn to graph horizontal and vertical lines.

Horizontal -- goes left to right (think horizon).

Vertical -- goes up and down.

Example 1:     Sketch the graph of x = 3.

When we graph in a coordinate plane we have two variables, x and y. 

For the equation x = 3, x is ALWAYS 3.  It doesn't make any difference what y is, x can only be 3. 

The equation x = 3 doesn't tell us anything about y.  It doesn't restrict y at all, so y can be any number.

Plot a few points with the x-coordinate always 3 and vary the y-coordinate.  Some examples are (3, -4), (3, -1), (3, 2), and (3, 5).

Draw a line with arrows through the points you plotted.  Make sure to label the points and the line.

Example 2:     Sketch the graph of y = -4.

For the equation y = -4, y is ALWAYS -4.  It doesn't make any difference what x is, y can only be -4. 

The equation y = -4 doesn't tell us anything about x.  It doesn't restrict x at all, so x can be any number.

Plot a few points with the y-coordinate always -4,  and vary the x-coordinate.  Some examples are (-4, -4), (-2, -4), (0, -4), and (3, -4).

Draw a line with arrows through the points you plotted.  Make sure to label the points and the line.