\begin{array}{|c|c|c|}\hline \text{70}&\text{2}\\\hline \text{35}&\text{5}\\\hline \text{7}&\text{7}\\\hline \text{1}&\text{}\\\hline\end{array}
$\text{nên 70 = 2 . 5 . 7 }$
\begin{array}{|c|c|c|}\hline \text{115}&\text{5}\\\hline \text{23}&\text{23}\\\hline \text{1}&\text{}\\\hline\end{array}
$\text{Nên 115 = 5 . 23}$
$\text{Vậy 70 = 2 . 5 . 7}$
$\text{115 = 5 . 23}$
