1,
\(a,35=5.7\\ 60=5.2^2.3\\ =>BC\left(35;60\right)=5.^{26}.7.3=420\\ b,28=2^2.7\\ 42=7.2.3\\ 56=7.2^3=>BC\left(28;42;56\right)=7.2^3.3=168\\ \)
2,
\(a,84=2^2.3.7\\ 64=2^6\\ =>ƯC\left(84;64\right)=2^2=4\\ b,256=2^8\\ 148=2^2.37=>ƯC\left(256;148\right)=2^2=4\)