Hướng dẫn trả lời:
Bài tập 7:
$\text{Câu a) 125.53 - 53.25.}$
$\text{= (125 - 25).53.}$
$\text{= 100.53.}$
$\text{= 5300.}$
$\text{Câu b) $5^9$ ÷ $5^7$ + 36 ÷ $3^2$ + $2018^0$.}$
$\text{= $5^9$ ÷ $5^7$ + $2^{2}.3^{2}$ ÷ $3^2$ + $2018^0$.}$
$\text{= $5^2$ + $2^{2}$ + $2018^0$.}$
$\text{= 25 + 4 + 1.}$
$\text{= 29 + 1.}$
$\text{= 30.}$
$\text{Câu c) 129 - 5.[29 - $(6 – 1)^{2}$].}$
$\text{= 129 - 5.(29 - $5^{2}$).}$
$\text{= 129 - 5.(29 - 25).}$
$\text{= 129 - 5.4.}$
$\text{= 129 - 20.}$
$\text{= 109.}$