Find the least squares approximating line
y = a0 + a1x for each of the following sets of data points.
(a) (1, 1), (3, 2), (4, 3), (6, 4)
(b) (2, 4), (4, 3), (7, 2), (8,1)
(c) (-1,-1), (0, 1), (1,2), (2, 4), (3, 6)
(d) (-2,3), (-1,1), (0, 0),(l,-2), (2,-4)