1. Writing Equations From Two Points

2. Table of Contents
26: Warm-Up, Guided Practice
27: How Do I Write an Equation From Two Points?

3. Warm - Up
Write an equation in slope-intercept form and point-slope form with the given information: 1. M = -6; (3, -2)
2. M = 0; (-7, 1)

4. Learning Intention/Success Criteria
LI: We are learning to write the linear equations using two points SC: I know how to -identify slope and y-intercept -use the slope formula to find slope -write linear equations in two ways

5. EQ: How Do I Write an Equation With Two Points?
5/14/2019

6. A number which is used to indicate the steepness of a line and if the line is tilted uphill or downhill
Slope
Indicated by the letter “m”
Point
The pair of numbers giving the location on a coordinate plane.
Written in the form: (x, y)

7. The point at which the function crosses the y-axis
Y-Intercept
Represented by the letter b
Slope Intercept Form
f(x) = mx + b
Slope Formula
m = y2 – y x2 – x1
Point Slope Form
y – y1 = m(x – x1)

8. Example 1: Find the equation of the line in slope intercept form that passes through (3, 1) and (-4, 15)
m = y2 – y x2 – x1
m = 15 – – 3
m =
m = -2
y = mx + b
1 = (3)(-2) + b
1 = -6 + b
+ 6
+ 6
______________
7 = b
y = -2x + 7

9. Guided Practice 1
Using slope-intercept form, find the equation of the line that passes through (2, -5) and (8, 13)
y = 3x - 11
Follow Up: What is f(-2) for this function?
f(-2) = -17

10. Guided Practice 2
Using slope-intercept form, find the equation of the line that passes through (4, -1) and (-2, 29)
y = -5x + 19
Follow Up: What is the value of x when f(x) = 9?
f(x) = 9 when x = 2.

11. Example 2: Find the equation of the line in point slope form that passes through (-2, -7) and (1, -1)
m = y2 – y x2 – x1
m =
m =
m = 2
y – y1 = m(x – x1)
y = 2(x – 1)
y + 1 = 2(x – 1)

12. Guided Practice 3
Find the equation of the line in point slope form that passes through (80, 198) and (150, 408)
y – 198 = 3(x – 80)
Follow Up: What is the equivalent equation in slope intercept form?
y = 3x - 42