2 Algebra 2 Lesson 1.3 Day 2 Linear Equations in two variables Parallel and Perpendicular Lines
3 Objectives:Write an equation for a line that is parallel or perpendicular to a given line.
4 Results from partner activity. Parallel LinesTwo lines that have the same slope are parallel.All horizontal lines are parallel.All vertical lines are parallel.Perpendicular LinesThe slopes of perpendicular lines are negative reciprocals of each other.All vertical lines are perpendicular to horizontal lines.All horizontal lines are perpendicular to vertical lines.
5 Practice: Identify parallel, perpendicular and intersecting Lines 1.) y = 2x+4 and y = -½x - 6Answer: Perpendicular lines2.) y = -3 and y = 4Answer: Parallel lines3.) y = 2x – 6 and x = 3Answer: Intersecting lines4.) y = ¼x + 7 and y + 4x = 25.) y -4x = 23 and 2y – 8x = 16Answer: Parallel lines
6 Key Concept: Use your knowledge of parallel and perpendicular slopes to write equations of line. You will still use the slope-intercept equation or the point-slope equation when writing the equations.
7 ExampleWrite in slope intercept form the equation of the line that is parallel to the linein the standard (x,y) plane anthat also contains the point (4, -2).1st step: find the slope2nd step: find the y-intercepty = mx+b-2 = (1/2)(4) +bb = -43rd step: write the equationy = (1/2)x - 4
8 Try TheseDirections: Write an equation in slope intercept form for the line that has the given information.Passing through (8, 5) and parallel toAnswer:Passing through (-2, -5) and perpendicular toContains the y-intercept of the line and is perpendicular to the line
9 Homework Lesson 1.3 Page 26 (35-51 odds, 53-58 all) Be sure to show all work and check your answers with b.o.b.