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4 tháng 1 2019

_____________________Giải_____________________

\(\hept{\begin{cases}a+2b⋮3\\3a+3b⋮3\end{cases}}\Rightarrow3a+3b-a-2b⋮3\Rightarrow2a+b⋮3\)

2. _____________________Giải________________________

\(\hept{\begin{cases}a-b⋮7\\7a+7b⋮7\end{cases}}\Rightarrow7a+a+7b-b⋮7\Rightarrow8a+6b⋮7\)

=> 2(4a+3b) chia hết cho 7  vì  (2;7)=1

=> 4a+3b chia hết cho 7 (đpcm)

14 tháng 2 2016

Dễ nhưng nhiều quá===>không làm

14 tháng 2 2016

giúp mình với ^^

9 tháng 10 2021

chia hết.chấm hếtttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt