1. 3-6:Slope of Parallel and Perpendicular Lines Objective: To relate slope of parallel and perpendicular lines, and to write equations of parallel and perpendicular lines.

2. (http://www.regentsprep.org/Regents/math/ALG EBRA/AC3/Lparallel.htm)

3. Slopes of Parallel Lines Slopes of parallel lines are equal Any 2 vertical lines are parallel; Any 2 horizontal lines are parallel Test whether 2 non-vertical or non-horizontal lines are || by comparing slopes EXAMPLE: l 1 contains points A(1,5) and B(3,1). l 2 contains points C(3,3) and D(1, -4) Are the 2 lines parallel? Explain.

4. Are the two lines parallel? Line 1 contains P(0,3) and Q(-2, 5) Line 2 contains R(0,-7) and S(3,-10)

5. Are the lines 4y-12x=20 and y=3x-1 parallel? Explain. Compare Slopes by re-writing in slope-intercept form:

6. Slope and Perpendicular Lines Perpendicular Lines have slopes that are opposite, reciprocals of each other Their slopes’ product is -1 Any vertical and any horizontal line are perp. Slope: Perpendicular Slope:

7. Are the 2 lines perpendicular? To answer this question, do the following: 1.Find their slopes 2.If their slopes are opposite, reciprocal, then they are perpendicular. Example: line 1: (-2,3) and (6, -3) line 2: (-3,-2) and (0,2)

8. Are the 2 lines perpendicular: 1. 2x-y=5 y= -1/2x +7 2.y=5 x=-2 3. -3x+y=5 3x –y =4

9. Writing Equations of Parallel Lines Write an equation of a line parallel to y=-2x +3 that contains the point (1, -2). Identify slope. Use this slope and given point to write equation:

10. Writing equations for perpendicular lines. 1.Identify slope of given line. 2.Find the slope of the line perpendicular to the given line (opposite, reciprocal) 3.Use the slope from step 2 and given point to write new equation.

11. Write the equation for the line perpendicular to y=-3x-5 that contains the point (-3, 7).

12. What do you see when you see an empty parrot cage? A polygon. HAHAHAHAHAHAHA………………………..