HOW TO FIND THE SLOPE OF A

LINE WHEN GIVEN 2 POINTS.

Simply put, find the difference of both the y and x coordinates and place them in a ratio.

The Slope of a line is the ratio of the change in y over the corresponding change in x.

y

mx

The formula frequently used to determine slope is:

2 1

2 1

y ym

x x

Because we are using two sets of ordered pairs both having x and y values, a subscript must be used to distinguish between the two values.

Let’s use the formula for finding the slope of a line given the points (3,2) and (1,4):

2 1

2 1

y ym

x x

Since (3,2) is our 1st ordered pair the coordinates are considered ,and since (1,4) is our 2nd ordered pair they are considered .

1 1( , )x y

2 2( , )x y

2 1

2 1

y ym

x x

So the slope of the line that these 2 points “sit on” is -1.

4 2

1 3m

21

2m

(3,2) and (1,4):

Got it?

1. Let’s use the formula for finding the slope of a line given the points

(19, -16) and (-7, -15):2 1

2 1

y ym

x x

15 16

7 ( 19)

So the slope of the line that these 2 points “sit on” is .

1

26

15 ( 16)

7 19m

1

26

1

26

As you can see we must be able to subtract integers to determine the slope of a line. So, let’s review.To subtract integers we rewrite as addition to add the opposite of the second integer. Then we follow the rules for adding integers.

When adding integers one of 2 things will occur. The signs will be alike or different.

If alike…add and use the sign.

If different, find the difference of their absolute values and use the sign of the larger absolute value.

2. Find the slope of a line given the points

(1, -19) and (-2, -7).

The slope is -4. Raise your hand if you got it!

Hooray!

3. Find the slope of a line given the points

(-4, 7) and (-6, -4).

The slope is . Raise your hand if you got it!

11

2

Cool!

Now, continue to use this formula to complete your worksheet. You’ve already done the first 3…