Graphing Linear Equations

1
Graphing Linear Equations

• Lesson 13.6
• Pre-AP Geometry

2
Lesson Focus

• The focus of this lesson is on the standard form
  and the slope-intercept form for the equation of
  a line.
• These forms are algebraic equations that
  describe geometric lines.

3
Standard Form

• The graph of any equation that can be written in
  the form
• Ax By C
• where A and B are not both zero, is a line.
• Graph the line by finding the x-intercept (a, 0)
  and y-intercept (0, b).

4
Slope-Intercept Form

• A line with the equation
• y mx b
• has slope, m and y-intercept, b.
• Graph the line by first plotting the y-intercept
  as the first point and allowing the slope to
  direct you to the second point.

5
Caution Vertical Lines

• Since a vertical line has undefined slope, we
  can not substitute a value for m into the
  slope-intercept equation.
• Instead, we must use the form x a.
• (where a is the x-coordinate of a point on the
  line).

6
Example 1

• On the same axes, graph y mx for m 3, -3,
  1/3, and -1/3.

7
Example 2

• Find the x- and y-intercepts of each line
• 3x 2y 6
• 2x y 4

8
Example 3

• Find the slope and y-intercept of each line
• x 2y 8
• 3x 4y 12

9
Written Exercises

• Problem Set 13.6, p.550 2 - 28 (even)
  Handout 13-6