1. Warm-Up 3/3/09 Graph the following equations 1. y = -2/3x + 2 m = ___ b = ___ 2. y = -2/3x – 3 m = ___ b = ___ What can you conclude about parallel lines and their slope?

2. Graph the following equations 1. y = 4x + 2 m = ___ b = ___ 2. y = -1/4x – 3 m = ___ b = ___ What can you conclude about perpendicular lines and their slope? Warm-Up 3/3/09

4. Parallel lines are always the same distance apart. They will never touch. “Enemy Lines” Parallel Lines

5. Intersecting Lines Intersecting lines are two lines that cross each other “Friends”

6. Perpendicular Lines Perpendicular lines are two lines that intersect to form right angles. 90 “Married”

7. Perpendicular lines are also intersecting lines because they cross each other. Perpendicular lines are a special kind of intersecting lines because they always form “perfect” right angles. 90

8. Write the equation of a line that is parallel to the line y = ½x – 7 and passes through the point (4, -2). Example 1 Step 1: Find the slope: The line parallel to y = ½x – 7 has the same slope, ½.

9. Replace m with ½ and (x, y) with (4, -2) in the slope-intercept form Step 2: Substitute the values for x and y to find b y = mx + b -2 = (1/2)(4) + b -2 = 2 + b b = -4 Step 3: Write the equation y = mx + b y = ½ x + (-4) OR y = ½ x – 4

10. Write the equation of the line parallel to the line 4x – 5y = 7 that passes through the point (-3, 7). y – y 1 = m(x – x 1 )

11. Write the equation of the line perpendicular to the line 3x + 2y = 9 that passes through the point (2, 5). y – y 1 = m(x – x 1 )