Question

How do you make a linear regression line from the data?

x: -4, -3, -2, -1, 0, 1, 2, 3, 4
y: 13, 7, 3, 1, 1, 3, 7, 13, 21

Answer 1

Plot the points and draw a "best fit" line through them. The linear regression is the equation for that line.

Explanation:

All statistics programs and even Excel can do that for you, including calculation of the "fit" of the line.

If you need to do it "manually" the physical graph may be a decent approximation. The most common mathematical approach is the "Least Squares Method" which calculates the "best fit" as a line that minimizes the average distance of the actual data points from the regression line.

https://www.easycalculation.com/analytical/learn-least-square-regression.php

http://www.stat.wmich.edu/s216/book/node126.html

This, and other methods are discussed here:
http://www.statisticssolutions.com/what-is-linear-regression/