a/
ta có
\(12=2^2.3\\ 80=2^4.5\\ 56=2^3.7\)
→ƯCLN(12,80,56)=\(2^2=4\)
b/
ta có
\(144=2^4.3^2\\ 120=2^3.3.5\\ 135=3^3.5\)
→BCNN(144,120,135)=\(2^4.3^3.5=2160\)
\(a,\) Ta có :
\(12=2^2.3\)
\(80=2^4.5\)
\(56=2^3.7\)
\(ƯCLN\left(12,80,56\right)=2^2=4\)
\(b,\) Ta có :
\(144=2^4.3^2\)
\(120=2^3.3.5\)
\(135=3^3.5\)
\(ƯCLN\left(144,120,135\right)=3\)