Câu 1:
\(\begin{array}{l}24 = {2^3}.3\\84 = {2^2}.3.7\\180 = {3^2}{.2^2}.5\\ \Rightarrow UCLN\,\,\left( {24;84;180} \right) = {2^2}.3 = 12\end{array}\)
Câu 2:
\(\begin{array}{l}24 = {2^3}.3\\40 = {2^3}.5\\168 = {2^3}.3.7\\ \Rightarrow BCBNN\left( {24,40,168} \right) = {2^3}.3.5.7 = 840\end{array}\)