Section 2 - Finding the Slope of a Line

Slope is most simply described as the tilt of a line. If you simplify it's formulas you find that it means the change in y divided by the change in x. The result of the formula gives you how many numbers the line goes up or down for each one point it moves to the right. Now here's the formula- (Y2-Y1) / (X2-X1). The 1 and 2 after the variable signify which point to take the numbers from. X1 and X2 are from the first point, and Y1 and Y2 are from the second point. Let's try it one time:

Point A - (1,3) Point B - (3,-6)

(-6-3) / (3-1)

-9 / 2

When you use slope, always leave your answers in a reduced fraction. So the slope of line AB is -9/2. If you have two parallel lines, their slopes are the same, and if you have two perpendicular lines, their slopes are negative reciprocals of each other. So a line perpendicular to one in the example would have a slope of 2/9. And if a line is horizontal, it has a slope of 0, if it is vertical, its slope is said as undefined. Not too tough, is it?

Use this image for number 1-5.

Find the slope of the following lines-

1) DA

2) CA

3) AB

4) EA

5) CB

Find the slope of a line perpendicular to a line with a slope of -

6) 1/2

7) -3/4

8) 8

9) 11/2

10) 6