INTERPRET LINEAR GRAPHS WRITE LINEAR EQUATIONS SECTION 5

INTERPRET LINEAR GRAPHS & WRITE LINEAR EQUATIONS SECTION 5. 4 B

The table below shows the total costs associated with purchases from an audio CD club, including and initial membership fee # of CD’s Total cost 0 2 4 6 8 $15 $25 $35 $45 $55 Plot the points on the coordinate plane and write the equation for this situation. 50 Slope = 5 y-intercept = 15 Equation: 40 30 2 10 20 Cost per CD: $5. 00 Membership fee: Membership fee 10 $15. 00 2 4 6 8 10

Example 1: A. The graph below shows the total costs associated with purchases from a DVD club, including an initial membership fee. Find the cost per DVD and the membership fee. Slope = 2. 5 Membership fee: $15. 00 50 4 40 10 Cost per DVD: $2. 50 15 Total cost ($) y-intercept = 30 20 10 2 4 6 8 # of DVD’s 10 12

B. The graph below shows the amount of money that David earns weekly at his job. David earns a certain amount per hour in addition to a base salary each week. Find his hourly pay and base salary. 180 Base salary: 8 160 140 120 100 80 60 40 20 40 TOTAL PAY Hourly pay: 4 8 12 16 # HOURS 20 24

If you know the _____ slope of the line and the coordinates of one points of its ______, you can write the equation for the line. When given the slope you must find the _______ y-intercept so that you can write the equation. Solve the following equation for b. You can use this formula to find b. You will then have enough information to write the equation in y = mx+b form.

1. Substitute the values for the slope and x and y. 2. Find the value of the y-intercept. 3. Write your equation in slope intercept form. Example 2: Write an equation in slope-intercept form that has the given slope and contains the given point. A.

B.

C.

D.

Example 3: On Monday a cylindrical storage silo was filled with grain to a certain height. On Tuesday the silo is then filled with more grain so that the height rises at a constant rate of 2 feet per minute. After 5 minutes the height of the grain is 15 feet. What was the height of the grain on Monday (initial height) before they began to fill it with more grain? Find the rate of change (slope): y-value x-value The grain was 5 feet tall when they began to fill the silo.