(a) Use m = 0 in Theorem 3 to show that the best-fitting horizontal line y = a0 through the data points (x1,y1),..., (xn,yn) is y = 1/n(y1+y2 + ∙ ∙ ∙ +yn), the average of the y coordinates.
(b) Deduce the conclusion in (a) without using Theorem 3.