I have a problem that i have troubles starting. I need to show if gcd(a, c)=1 and c divides ab, then c divides (ab + bx). My prof gave us a hint to use Euclid's lemma, which states if a divides bc and gcd(a, b) = 1 then a divides c.
Edit: Ok, so i figured that, from Euclid's lemma we can get that c divides b, but now im stuck again
Thank you in advance.