1. Lesson 4-9 Slopes of Parallel and Perpendicular Lines
Obj: The student will be able to 1) Identify and graph parallel and perpendicular lines 2) Write equations to describe lines parallel or perpendicular to a given line HWK: p all, all, 25, 27, 31, 34, 36, 40, 48 Vocab: 1) parallel lines 2) perpendicular lines

2. Parallel Lines All different vertical lines are parallel
Two different nonvertical lines are parallel if and only if they have the same slope

3. Identify which lines are parallel
Ex 1) y = x y = y = x – y = -3

4. Ex 2) y = 3x + 2; y = - 1 2 x + 4 ; x + 2y = -4; y – 5 = 3(x – 1)

5. Ex 3) Show that ABCD is a parallelogram

6. Perpendicular Lines
Vertical lines are perpendicular to horizontal lines
Two nonvertical lines are perpendicular if and only if the product of their slopes is -1

7. Ex 4) Identify which lines are perpendicular
y = y – 6 = 5(x + 4) x = y = x + 2

8. Ex 5) Show that P(1, 4), Q(2,6) and R(7,1) are the vertices of a right triangle

9. Write an equation in slope-intercept form for the line that passes through the given point and satisfies the given condition
Ex 6) passes through (5, 7) and parallel to the line described by y = x - 6

10. Ex 7) passes through (-5, 3) and perpendicular to the line described by y = 5x