SLOPE AND Y-INTERCEPT FORMLesson 5-3

An equation in the form of ______________ is in ________-_______________ form.

_________ _________

y = mx + b

slopeintercept

slope

y - intercept

y = 4x – 5

y = 4x + 6

-3

y = 2x – 3

3

y = – 2x + 3

II. Write an equation in slope-intercept form for each graph.

-7

(0, -7)

up 1 right 2

Graph (0, -4). Find additional points by going up 2 and right 1.

Graph (0, 5). Find additional points by going up 3 and left 4 OR down 3 and right 4.

5x – 5x + 4y = 8 – 5x

4y = 8 – 5x

(0, 2)

3x – 3x + 2y = 6 – 3x

2y = 6 – 3x

3

V. Write an Equation in Slope-Intercept Form  

Suppose you have already saved $50 toward the cost of a new television set. You plan to save $5 more each week for the next several weeks. 

What is your starting point? _______

(This will be your _______________.)

What action is being repeated? _____________________

(This becomes the ____________________.)

Write the equation ________________________

$50

y - intercept

Saving $5 each week

slope

y = 5x + 50

Practice: Write an equation in slope-intercept for each situation. 14. A video store charges $15 for a rental card plus $1.50 per rental.  15. A Norfolk pine is 22 inches tall and grows at a rate of 1.4 feet

per year. (Careful, all units must be the same!)  16. A terrier weighs 32 pounds and is on a special diet to lost 3 pounds per month.

17. An airplane at an altitude of 2000 feet ascends at a rate of 750 feet

per mile.

 

WRITING AN EQUATION GIVEN TWO POINTS. (You must write these on your own paper.)

Directions: Write an equation in slope-intercept form that passes through the line containing the two points given.

M. (-2, 4) and (3, -1)

Step 1: Find the slope.

Step 2: Find the y-intercept (b)

Substitute a point in the equation and solve for “b”

y = mx + b

4= (-1)(-2) + b

4= 2+ b

4 - 2= 2 - 2+ b

2= b

Step 3: Write the equation substituting the value of m and b

y = mx + by = -1x + 2y = -x +2

N. (-2, -1) and (4, 2)

Step 1: Find the slope.

Step 2: Find the y-intercept (b)

Substitute a point in the equation and solve for “b”

y = mx + b

2= (1/2)(4) + b

2= 2+ b

2 - 2= 2 - 2+ b

0= b

Step 3: Write the equation substituting the value of m and b

y = mx + by = ½ x + 0y = ½ x

O. (-6, 5) and (1, 0)

Step 1: Find the slope.

Step 2: Find the y-intercept (b)

Substitute a point in the equation and solve for “b”

y = mx + b

0= (-5/7)(1) + b

0= -5/7+ b

0 + 5/7= -5/7 + 5/7 + b

5/7= b

Step 3: Write the equation substituting the value of m and b

y = mx + by = -5/7x + 5/7

P. (2, -6.9) and (-4, 4.6)

Step 1: Find the slope.

Step 2: Find the y-intercept (b)

Substitute a point in the equation and solve for “b”

y = mx + b

6.9= (1.15)(-2) + b

6.9= -2.3+ b

6.9 + 2.3= -2.3 + 2.3 + b

9.2= b

Step 3: Write the equation substituting the value of m and b

y = mx + by = 1.15x + 9.2

Virtual Nerd on Slope-Intercept Form

Watch these videos to help you understand slope-intercept form.

Homework Tutor - Writing Equations in Slope-Intercept form

Homework Tutor - Graphing a Line Using Slope Intercept Form

Homework Tutor - Equations from Graphs