Đáp án:
7) 0
Giải thích các bước giải:
\(\begin{array}{l}
5)\dfrac{{70}}{3}:\left( { - \dfrac{5}{7}} \right) - \dfrac{{40}}{3}:\left( { - \dfrac{5}{7}} \right)\\
= \left( {\dfrac{{70}}{3} - \dfrac{{40}}{3}} \right):\left( { - \dfrac{5}{7}} \right)\\
= 10:\left( { - \dfrac{5}{7}} \right) = - 14\\
6)\dfrac{{{2^{12}}{{.3}^5} - {2^{2.6}}{{.3}^6}}}{{{2^{12}}{{.3}^{2.3}} + {2^{3.4}}{{.3}^5}}}\\
= \dfrac{{{2^{12}}{{.3}^5}\left( {1 - 3} \right)}}{{{2^{12}}{{.3}^5}\left( {3 - 1} \right)}} = - \dfrac{2}{2} = - 1\\
7)\left( { - \dfrac{3}{4} + \dfrac{2}{7} - \dfrac{1}{4} + \dfrac{5}{7}} \right):\dfrac{2}{3}\\
= 0.:\dfrac{2}{3} = 0
\end{array}\)
