4 1 Writing Linear Equations in SlopeIntercept Form

4 -1 Writing Linear Equations in Slope-Intercept Form Goals: • Use the slope and y-intercept to write the equation of a line. • Model a real-life situation with a linear equation. Eligible Content: A 1. 1. 2. 1. 1 / A 1. 1. 2. 1. 3 / A 1. 2. 1. 1. 1 / A 1. 2. 2. 1. 3 / A 1. 2. 2. 1. 4

Example Write the equation of the line whose slope is -2 and whose y-intercept is 5. b m y = mx + b y =-2 x +5 y = -2 x + 5

Examples Write an equation in slope-intercept form. 1. Slope is 3, y-intercept is -5 y = 3 x – 5 2. m = -3, b = 6 y = -3 x + 6 3. Slope is – ½, y-intercept is -4 y=-½x– 4

Write an equation in slope-intercept form of the line whose slope is 4 and whose y-intercept is 3. A. y = 3 x + 4 B. y = 4 x + 3 C. y = 4 x D. y = 4

Write the equation of each graph. 1. 2.

Example #3 Which of the following is an equation in slope-intercept form for the line shown in the graph? A. B. C. D.

Which of the following is an equation in slopeintercept form for the line shown in the graph? A. B. C. D.

Practice Write an equation in slope-intercept form. 1. m = 5, b = 8 2. Slope is 6, y-intercept is – 3 3. b = 4, m = ¼ 4. y-intercept is 2, slope is -6 5. m = 1, b = 0 1. y = 5 x + 8 2. y = 6 x – 3 3. y = ¼ x + 4 4. y = -6 x + 2 5. y = x

Word Problems �Slope is rate of change!!! �Look for words like per, for each, for every… �y-intercept is the beginning amount �Look for words like beginning, initial…

Word Problem #1 Your family decides to rent bikes while you are on vacation. It costs $4 to rent the bike, plus $1. 50 per hour. �Write an equation in slope-intercept form that models this situation. y = 1. 5 x + 4 �How much will it cost to rent the bike for 12 hours? $22

Word Problem #2 In 1990, the population in California was 29. 76 million. During the next 25 years, the population increased by. 31 million people per year. �Write an equation in slope-intercept form that models this situation. y =. 31 x + 29. 76 �How many people were there in California in 2005? 34. 41 million people

Word Problem #3 A telephone call costs $3. 44 for the first minute, and $. 24 for each additional minute. �Write an equation in slope-intercept form that models this situation. y =. 24 x + 3. 44 �How much will it cost for a 9 minute phone call? $5. 36

The amount of money spent on Christmas gifts has increased by an average of $150, 000 ($0. 15 million) per year since 1986. Consumers spent $3 million in 1986. Write a linear equation to find the average amount D spent for any year n since 1986. A. D = 0. 15 n B. D = 0. 15 n + 3 C. D = 3 n D. D = 3 n + 0. 15

The amount of money spent on Christmas gifts has increased by an average of $150, 000 ($0. 15 million) per year since 1986. Consumers spent $3 million in 1986. Find the amount spent by consumers in 1999. A. $5 million B. $3 million C. $4. 95 million D. $3. 5 million

Homework �Pages 220 -221 #11 -22 #37, 50, 51 You do not have to graph any equations!