1.Show gcd(a,b,c) = gcd(a, gcd(b,c)) 2. Relevant equations 3. My attempt is that gcd(a,b,c) can be written as the product of their prime factors. Lets say x is that product. The thing is, I know how to prove this using prime factorization but there has to be another method concerning linear combinations. Like gcd(a,b,c) = ax + by+ cz.