Slope from Two Points

Lesson 2.5 - Finding slope with two points

Learning Intention: I can determine the equation of a line in slope-intercept form given two points by determining the slope and algebraically solving for the y-intercept.

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​STANDARD: 8.F.4

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​Success Criteria:

• ​I can determine the constant rate of change when given two ordered pairs.

• ​I can find the y-intercept algebraically when given a slope and ordered pairs.

• ​I can determine a linear equation in slope intercept form when given two ordered pairs.

​How to Find the Slope when Given Two Points

• ​We can find the slope of a line if we are only given two points!!

• ​We use the y-values and x-values to find the change in y and the change in x.

• ​The slope formula is pictured to the right!

​But what is this y₂, y₁, x₂, and x₁??

• ​x₁ AND y₁ come from the first point listed

• ​x₂ AND y₂ come from the second point listed

Multiple Choice

Which number represents the y₂?

(2, 1) (5, -8)

• 2

• 1

• 5

• -8

Multiple Choice

Which number represents the x₁?

(2, 1) (5, -8)

• 2

• 1

• 5

• -8

Multiple Choice

Which number represents the x₂?

(3, 5) (18, -39)

• 3

• 5

• 18

• -39

Multiple Choice

Which number represnets the y₁?

(3, 5) (18, -39)

• 3

• 5

• 18

• -39

​How to substitute into the slope formula

1. ​Identify the (x₁, y₁) AND (x₂, y₂).

2. Substitute into the formula.

3. Simplify the numerator and denominator.

4. Simplify the fraction as needed.​

Multiple Choice

True or False: To find the slope between the points (3, 4) and (5, 2) you would do the following

• True

• False

Multiple Choice

True or False: To find the slope between the points (2, -7) and (1, 3) you would do the following

• True

• False

Open Ended

CHALLENGE: Use the two points to write the equation of the line in slope-intercept form.

(-6, 5) (-3, -3)

**Type your answer in the form y=mx+b