writing linear equations

[jmozley]

okay so heres the problem i cant figure out how to find the slop or any of the equation i have the answer i just dont know how to get to it??

1. Business: In 1999, there were 4076 J.C. Penney stores and in 2003, there were 1078 stores. Write a linear equation that gives the number of stores in terms of the year. Then, predict the number of J.C. Penney stores in 2010. Is your answer reasonable? Explain.

answer is 2. y = -749.5(x – 1999) + 4076 Prediction y = -4168.5, this answer is not reasonable since you can not have less than 0 stores

 

[Mrspi]

okay so heres the problem i cant figure out how to find the slop or any of the equation i have the answer i just dont know how to get to it??

1. Business: In 1999, there were 4076 J.C. Penney stores and in 2003, there were 1078 stores. Write a linear equation that gives the number of stores in terms of the year. Then, predict the number of J.C. Penney stores in 2010. Is your answer reasonable? Explain.

answer is 2. y = -749.5(x – 1999) + 4076 Prediction y = -4168.5, this answer is not reasonable since you can not have less than 0 stores

Do you realize that the problem is giving you TWO points on a line? The points are in the form (year, number of stores).

The first point is (1999, 4076).
The second point is (2003, 1078)

Remember how to find the slope of the line through two points (x₁, y₁) and (x₂, y₂)?

m = [y₂ - y₁] / [x₂ - x₁]

Use your two points:

m = (1078 - 4076) / (2003 - 1999)

m = (-2998) / 4

m = -749.5

That's how they got the slope in the answer.

Now, you can use that slope and ONE of the points to find the y-intercept....

And then you can write the equation.

Please show us what you can do with the rest of the problem. I don't generally GIVE answers, especially when I have no idea where you are "stuck".