Unit 5
Day 5:
Students will be able to write an equation of a line given data points.
Writing the equation of a line given only the data points would be to create an equation using only points on a graph such as (2, 4) and (8, 12). If given data points such as (2, 4) and (8, 12), the first thing you would want to do is minus the Y from the 2nd point from the Y in the 1st point. Then do the same with the X's. Write the Y number over the X number. You will now get a fraction of 8/6. This is your slope in the equation; it can be changed from the 8/6 fraction to a 1 1/3 fraction (y = 1 1/3x + b). From here you would take on the points given to you originally and put it into the equation and minus the two numbers. y(4) - 1 1/3(2) = 1 1/3. This number is now your B in the equation (y = 1 1/3x + 1 1/3)
Quiz
1. Using the points (4,3) and (-4,-2) write a y=mx+b equation.
2. Using a slope of 4 and the points (1,2) determine a y=mx+b equation.
3. Using the points (4,8) and (1,5) write an y=mx+b equation.
Answers
1. Follow the steps from above and you should have an answer of: y = .625x + .5
2. Plug in the slope given to get an equation of y = 4x + b Next plug in the point given to find "b", 2 - 4(1) = -2. The final equation should be: y = 4x - 2
3. Following the same steps used in Question #1, your equation should be: y = x + 4
Tips From the Pros
Writing the equation of a line given only the data points would be to create an equation using only points on a graph such as (2, 4) and (8, 12). If given data points such as (2, 4) and (8, 12), the first thing you would want to do is minus the Y from the 2nd point from the Y in the 1st point. Then do the same with the X's. Write the Y number over the X number. You will now get a fraction of 8/6. This is your slope in the equation; it can be changed from the 8/6 fraction to a 1 1/3 fraction (y = 1 1/3x + b). From here you would take on the points given to you originally and put it into the equation and minus the two numbers. y(4) - 1 1/3(2) = 1 1/3. This number is now your B in the equation (y = 1 1/3x + 1 1/3)
Quiz
1. Using the points (4,3) and (-4,-2) write a y=mx+b equation.
2. Using a slope of 4 and the points (1,2) determine a y=mx+b equation.
3. Using the points (4,8) and (1,5) write an y=mx+b equation.
Answers
1. Follow the steps from above and you should have an answer of: y = .625x + .5
2. Plug in the slope given to get an equation of y = 4x + b Next plug in the point given to find "b", 2 - 4(1) = -2. The final equation should be: y = 4x - 2
3. Following the same steps used in Question #1, your equation should be: y = x + 4
Tips From the Pros
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