E B = E Zi( xi - x) yi Ei (xi - X) . E(yi) E. (xi - x) 2 since the xis are known Ci (xi - 8)2 Ei (xi - X) . E (Bo + Bixi) (xi - X) = ( xi - x)2 ci (Bo + Bixi) , where c = E. ( x - 8) 2 = Bo [ cit BI _ cixi = B1 where the last result is true since _, c; = 0, and _, cix; = 1