How can I prove that if x is a great enough positive integer divisible by [math] \gcd(a_1,a_2, \ldots,a_n) [\math] then there exist POSITIVE integers [math] x_1, x_2, \ldots, x_n [\math] such that [math] a_1x_1+a_2x_2+ \ldots a_nx_n = x [\math]?
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