I want to show that $a \mid bc$ implies $a \mid \gcd(a,b)\times \gcd(a,c)$.
My answer: since $$ a\mid ac \quad \text{ and } \quad a\mid bc,$$ we get that $a \mid \gcd(ac,bc)$ which implies that $$ a \mid |c|\gcd(a,b).$$
However, I don't know the final step.
Recall that the $gcd$ is a linear combination. i.e. $(a,b)(a,c)$ can be written as
$$(a,b)(a,c)=(am+bn)(ak+cl)=a^2mk+amcl+bnak+bncl$$
$$=a(amk+mcl+bnk) + bc(nl)$$
If $a\mid bc$ then $a$ divides the right hand side.