S LOPE AND Y -I NTERCEPT F ORM Lesson 5-3

An equation in the form of ______________ is in ________- _______________ form. _________ y = mx + bslope intercept 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 1right 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 = 5 x + 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= b 2= b Step 3: Write the equation substituting the value of m and b y = mx + b y = -1x + 2 y = -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= b 0= b Step 3: Write the equation substituting the value of m and b y = mx + b y = ½ x + 0 y = 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 + b y = -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= b = b 9.2= b Step 3: Write the equation substituting the value of m and b y = mx + b y = 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