3-6 Writing Equations of Parallel and Perpendicular Lines LEQ: How do you write equations for lines that are parallel or perpendicular to a given line?

Parallel Slope Property: Two nonvertical lines are parallel if and only if their slopes are equal. Any 2 vertical lines are parallel.

Determining whether lines are parallel. Are the lines in the figure below parallel? Explain. Yes, b/c they both have the same slope.

What do you need in order to be able to write an equation of a line? The slope of the line. A point that the line goes through.

Writing an Equation of a Parallel Line. Write an equation for a line that contains (- 2, 3) and is parallel to the graph of 5x – 2y = 8. Step 1: Find the slope of your new line.

Step 2: Use your new slope and the given point to write an equation in point-slope form.

Perpendicular Slope Property: Two nonvertical lines are perp. iff the product of their slopes is -1. The slopes of 2 perp. lines are opposite reciprocals. Any vertical and horizontal line are always perp.

Checking for Perpendicular Lines. Prove that the lines in the figure below are perpendicular. Blue Line: m = Red Line:

Writing an Equation of a Line Perpendicular to a Given Line. Write the equation of the line that passes through the point (0, 4) and is perpendicular to y = 2x – 3. Step 1: Find the slope of your new perp. line.

Step 2: Use your new slope and the given point to write your equation in point-slope form.

Closure: Describe the slopes of parallel lines. Describe the slopes of perpendicular lines.

Homework: Pg 161-162 #s 2 – 30 even. Pg 161-162 #s 2 – 30 every other even.