Find the equations of the planes that passes through three points (a)
(1, 1, – 1),  (6, 4, – 5), (– 4, – 2, 3)
(b)
(1, 1, 0), (1, 2, 1), (– 2, 2, – 1)
7 Find the intercepts cut off by the plane 2x + y – z = 5 8