Đáp án:
2b) -5750
4) 8;10;20;40
Giải thích các bước giải:
\(\begin{array}{l}
2b)\, = 45\left( {25 - 75} \right) - 35\left( {78 + 22} \right)\\
= 45\left( { - 50} \right) - 35.100\\
= - 2250 - 3500\\
= - 5750\\
4)\,de\,bai\, \Rightarrow \,120\, \vdots \,a;\,80\, \vdots \,a\\
\Rightarrow a\, \in \,UC\left( {120;80} \right),\,a > 5\\
80 = {2^4}.5\\
120 = {2^3}.3.5\\
\Rightarrow UCLN\left( {80;120} \right) = {2^3}.5 = 40\\
\Rightarrow a \in U\left( {40} \right) = \left\{ {1;2;4;5;8;10;20;40} \right\},a > 5\\
\Rightarrow a \in \left\{ {8;10;20;40} \right\}
\end{array}\)
