1. 1.1 Lines in a Plane Finding the slope of a line
Using Point-Slope form of the equation of a line
Using Slope-Intercept form of the equation of a line
Using General (Standard) form of the equation of a line
Finding the equations of parallel and perpendicular lines

2. The slope m of a line through the points

3. Example 1
Find the slope of the line passing through each pair of points
(-2,0) and (3,1)

4. Find the slope of the line containing (-1,2) and (2,2)

5. Find the slope of the line containing (0,4) and (1,-1)

6. Student Example
Find the slope of a line containing the points (-4,6) and (5,-2)

7. Lines may take 4 different forms:
Positive Slope Negative Slope
Slope of Zero Undefined Slope

8. The Point-Slope Form of a Line The line passing through the point and has a slope of m can be written

9. Example 2
Find an equation of a line that passes through the point (1,-2) and has a slope of 3.

10. Slope-Intercept Form
y=mx+b where m is the slope and (0,b) is the y-intercept
Give the equation of a line passing through the point (1,-2) and has a slope of 3.

11. Student Example
Find an equation of a line that passes through the point (2,-4) and has a slope of –2.
Give the equation in point-slope form
Give the equation in slope-intercept form

12. Example 3
During 2000, Nike’s net sales were $9 billion, and in 2001 net sales were $9.5 billion. Write a linear equation giving the net sales y in terms of the year x. Then use the equation to predict the net sales for 2002.

13. Example 4
Determine the slope and the y-intercept of each linear equation.
a. x+y=2 b. y=2

14. Example 5
The graphs of y=-x-1 and y=-10x-1 are shown on p. 8. What is different about the graphing calculator that would make both graphs appear the same?

15. Example 6
Find the slope-intercept form of the equation of the line that passes through the point (2,-1) and is parallel to the line 2x-3y=5.
*Hint – Parallel lines have the same slope

16. Student Example
Find the slope-intercept form of the equation of the line that passes through the point (-2,4) and is parallel to the line x-2y=5.

17. Example 7
Find the slope-intercept form of a line that passes through the point (2,-1) and is perpendicular to the line 2x-3y=5
*Hint – Perpendicular lines have opposite reciprocal slope

18. Student Example
Find the slope-intercept form of the equation of the line that passes through the point (-2,4) and is perpendicular to the line x-2y=5.

19. Example 8
Graph the lines y=x+1 and y=-x+3 on your graphing calculator. If these lines are suppose to be perpendicular, why don’t they appear as such on your calculator screen?

20. p. 11-12, 1st problem in each section p. 13-14 #65, 69, 71, 75-79