1. 3.7-3.8 Equations of Lines in the Coordinate Plane and Slopes of Parallel and Perpendicular Lines
Objective: Students will find the slopes of lines and use slope to identify parallel and perpendicular lines.

2. Definitions and Postulates
Slope:
Two nonvertical lines have the same slope if and only if they are parallel
Two nonvertical lines are perpendicular if and only if the product of their slopes is -1
Slopes are opposite reciprocals.

3. Examples Find the slope of each line. 1. (-3,7) and (-1,-1)
Determine whether line FG and line HJ are parallel, perpendicular, or neither.
1. F(-1,3), G(-2,-1), H(5,0), J(6,3)
2. F(4,2), G(6,-3), H(-1,5), J(-3,10)
3. F(-3,-2), G(9,1), H(3,6), J(5,-2)

4. Equations of Lines Slope-Intercept Form: Point-Slope Form:
where m = slope and b = y-intercept
Point-Slope Form:
where m = slope, y1 = y coordinate, x1 = x coordinate.

5. Writing equations given a slope and a y-intercept
Write an equation in slope-intercept form for the given information.
m = 6, y-intercept = -3
m = -1/2 , y-intercept = 4

6. Write an equation of a line given a slope and a point
Write an equation in point-slope and slope-intercept form using the given information.
m = -3/5, (-10,8)
m = 3, (4,-1)

7. Write an equation of a line given 2 points
Write an equation of the line in slope-intercept form given 2 points.
(4,9) and (-2,0)
(3,-1), (7,-1)
(2,5), (2,-10)

8. Write equations of parallel and perpendicular lines
Write an equation in slope-intercept form for the given information.
A line parallel to and contains (7,-2).
A line perpendicular to and contains (-2,-3).