1. 2.5 Writing Equation of a Line Part 2 September 21, 2012

2. In a coordinate plane, 2 lines are parallel if and only if they have the same slope. Slopes of Parallel Lines

3. Write Equations of Parallel Lines – The given line has a slope of 2. Any line parallel to this line will also have a slope of 2. – Write an equation of the line that passes through and is parallel to the line. 5 = 2x2xy+ – () 4 1,1, – y = mx + b 4 =-2(-1) + b 4 = 2+ b -2 2 = b y = -2x + 2 Simplify Solve for b Substitute 4 for y, -1 for x and -2 for m

4. Another Example Find the equation of a line going through the point (3, -5) and parallel to Using the point-slope equation where the slope m = - 2 / 3 and the point is (3, -5) we get OR

5. Find the equation of the line going through the point (4,1) and parallel to (click mouse for answer) Find the equation of the line going through the point (-2,7) and parallel to (click mouse for answer) Checkpoint

6. In a coordinate plane, 2 lines are perpendicular if and only if their slopes are opposite reciprocal of each other (or their product is –1) Slopes of Perpendicular Lines

7. Find the equation of a line going through the point (3, -5) and perpendicular to The slope of the perpendicular line will be m = 3 / 2. Using the point-slope equation where the slope m = 3 / 2 and the point (3, -5) we get Equation of a line Perpendicular to another line

8. Find the equation of the line going through the point (-6, -5) and perpendicular to y = -x + 2. Find the equation of the line going through the point (-2,7) and perpendicular to Checkpoint 1 = xy+

9. Homework : 2.5 p.98 #37-42ALL, 44-50even