The formula for the least-squared regression line is in the following form:  y = a + bx

             where:

                          `b = (  (sum(XY) - (sumX * sumY)"/n")) / (sum(X^2) - (sumX)^2"/n")`
             and
                            `a = MY - b*MX`           

MY is mean of Y.  MX is mean of X.

To compute the least squares trend line for a set of values, CLICK HERE.