- #1
chaotixmonjuish
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If a|(b+c) and gcd(b,c)=1, then gcd(a,b)=1=gcd(a,c)
Suppose a|(b+c) and the gcd(a,b)=d.
al=b+c and d|a and d|b. This implies a=dr and b=ds.
drl=ds+c => drl-ds=c => d(rl-s)=c => d|c
Since d|b, d|c and 1|b and 1|c, d must divide 1. Therefore d=1.
By the same reasoning gcd(a,c)=1.
al=b+c and d|a and d|c. This imples a=dr and c=dt
drl=b+dt => drl-dt=b => d(rl-t)=b => d|b
since gcd(b,c)=1 1|b and 1|c and d|c d must divide 1
therefore d=1
Suppose a|(b+c) and the gcd(a,b)=d.
al=b+c and d|a and d|b. This implies a=dr and b=ds.
drl=ds+c => drl-ds=c => d(rl-s)=c => d|c
Since d|b, d|c and 1|b and 1|c, d must divide 1. Therefore d=1.
By the same reasoning gcd(a,c)=1.
al=b+c and d|a and d|c. This imples a=dr and c=dt
drl=b+dt => drl-dt=b => d(rl-t)=b => d|b
since gcd(b,c)=1 1|b and 1|c and d|c d must divide 1
therefore d=1