$\text{Bài tập 1:}$
$\text{Phân tích: (Xem hình).}$
$\text{Do đó: 120 = 2.2.2.3.5 = $2^3$.3.5.}$
$\text{Bài tập 2:}$
$\text{a) 4.$5^2$ - $3^2$.($2009^0$ + $2^3$).}$
$\text{= $2^2$.$5^2$ - $3^2$.(1 + 8).}$
$\text{= $(2.5)^2$ - $3^2$.9.}$
$\text{= $10^2$ - $3^2$.$3^2$.}$
$\text{= $10^2$ - $(3.3)^2$.}$
$\text{= $10^2$ - $9^2$.}$
$\text{= 100 - 81.}$
$\text{= 19.}$
$\text{b) 125 - 2.[56 - 48 ÷ (15 - 7)].}$
$\text{= 125 - 2.(56 - 48 ÷ 8).}$
$\text{= 125 - 2.(56 - 6).}$
$\text{= 125 - 2.50.}$
$\text{= 125 - 100.}$
$\text{= 25.}$
$\text{c) 25.27 + 45.27 + 27.30.}$
$\text{= 27.(25 + 45 + 30).}$
$\text{= 27.100.}$
$\text{= 2700.}$
