Đáp án:
2) x=12
Giải thích các bước giải:
Em tách hỏi từng câu thôi nhé
\(\begin{array}{l}
2)\, \Rightarrow 24\, \vdots \,x\,va\,\,36\, \vdots \,x\,\,\left( {x > 9} \right)\\
\Rightarrow x \in UC\left( {24;36} \right)\\
24 = {2^3}.3\\
36 = {2^2}{.3^2}\\
\Rightarrow UCLN\left( {24;36} \right) = {2^2}.3 = 12\\
\Rightarrow UC\left( {24;36} \right) = U\left( {12} \right) = \left\{ {1;2;3;4;6;12} \right\}\\
ma\,x > 9 \Rightarrow x = 12\\
3)\,A \cap B = \left\{ {1;4} \right\}\\
4)\,360 = {2^3}{.3^2}.5\\
8400 = {2^4}{.3.5^2}.7\\
\Rightarrow BCNN\left( {360;8400} \right) = {2^4}{.3^2}{.5^2}.7 = 25200\\
144 = {2^4}{.3^2}\\
420 = {2^2}.3.5.7\\
252 = {2^2}{.3^2}.7\\
\Rightarrow BCNN\left( {144;420;252} \right) = {2^4}{.3^2}.5.7 = 5040
\end{array}\)
