... next-to-last equation, a, is a linear combination, with integer coefficients, of a, -l and an -2 . Again working backwards we see that a, is a linear combination of a, -i and an-i ... divide a by al and continue the process until some remainder, a, +l , equals 0. a = qlal + a2 a1 = q 2a2 + a3 an -2 = qn-1G-1 + an an-i = qnan. This must occur, since a > ... equations we find that a, la, -2 , anlan-3 , . . . , anla and a, \b. Thus a, is a common divisor of a and b and a, 5 g (the greatest). With Eq. (6) we therefore obtain Eq....