Prove that if gcdb c 1 then gcda bc gcda bgcda cSolutionUs
Prove that if gcd(b, c) = 1, then gcd(a, bc) = gcd(a, b)gcd(a, c)
Solution
Using Bezout\'s Identity:
Since there are x,y,u,v so that ax+by=1 and au+cv=1 , we have
bycva(x+u?axu)+bcvy =(1?ax)(1?au)=1?a(x+u?axu)=1
Therefore, (a,bc)=1
Since a,b are relatively prime, there exist integers x,y such that ax+by=1 . Multiplying both sides of this equation by c , we get
acx+bcy=c.
| Using Bezout\'s Identity: Since there are x,y,u,v so that ax+by=1 and au+cv=1 , we have bycva(x+u?axu)+bcvy =(1?ax)(1?au)=1?a(x+u?axu)=1 Therefore, (a,bc)=1 
 | 

