That is the the basic form of linear regression by hand. Note that there ARE other ways to do this - more complicated ways (assuming different types of distributions for the data).

CBSE 12th Maths Linear Programming Formulas: Check here for all the important formulas of mathematics in Chapter 12 Linear Programming of Class 12, along with major definitions, theorems and examples.

Pamela J. Wells, Understanding Linear Functions and Their Representations, Mathematics Teaching in the Middle School, Vol. 21, No. 5 (December 2015/January 2016), pp. 308-316 ...