Drill #20*

Find the slope of the line passing through the following points:

1. ( 3, 6) , ( 7, 9)

2. ( -1, -2 ) , ( 4, 5 )

3. ( 4, 2 ) , ( -2, -5 )

Slope (20.)**

Slope: The ration of the change in vertical units to the change in horizontal units (RISE OVER RUN).

The formula for the slope m of the line passing through and

is given by .

That is the change in the y coordinate (RISE) over the change in the x coordinate (RUN)

),( 11 yx ),( 22 yx

12

12

xx

yym

Slope (#20*)

Determine the value of r so that a line through the points has the given slope:

4. (3, r ) , ( -2, 1 ) m = 2

5. ( -3 , 6) , ( r, 12) m = -¾

Parallel Lines (21. & 22.) **

Parallel Lines: In a plane, non-vertical lines with the same slope are parallel.

Perpendicular Lines: In a plane, two oblique lines are perpendicular if and only if the product of their slopes is -1.

Parallel and Perpendicular Lines

Parallel Lines• Have the same slope.• To determine if two lines are parallel, find the slope

of both lines. If they are the same they are parallel.

Perpendicular Lines• Product of slopes is -1• To determine if two lines are perpendicular, find the

slope of both lines. Multiply the slopes together. If the product is -1 they are perpendicular.

Determine if the following lines are parallel, perpendicular, or neither:

6. y = 3x + 3y = -3x – 1

7. y = -2x + 1y = ½ x – 2

8. y = 2y = -½