Example 4.  Computer derivation of the coefficients a and b for the "normal equations" for "Least Squares Lines"  .  
Solution 4.

Divide each summation term by 2.

Expand the terms in the first equation.

Distribute the summation over the term and obtain the "normal equations" for "Least Squares Line"  .

Solve for  a  and  b.

(c) John H. Mathews 2003