1- \(\left(5\frac{4}{9}+x-7\frac{7}{18}\right):15\frac{3}{4}\)= 0
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\(a)\frac{\left(\frac{3}{10}-\frac{4}{15}-\frac{7}{20}\right).\frac{5}{19}}{\left(\frac{1}{14}+\frac{1}{7}-\frac{-3}{35}\right).\frac{-4}{3}}\)\(=\frac{\frac{-19}{60}.\frac{5}{19}}{\frac{3}{10}.\frac{-4}{3}}=\frac{5}{24}\)
Hok tốt
\(\left( {\dfrac{1}{7}x - \dfrac{2}{7}} \right)\left( {\dfrac{{ - 1}}{5}x + \dfrac{3}{5}} \right)\left( {\dfrac{1}{3}x + \dfrac{1}{3}} \right) = 0\\ \Leftrightarrow \left[ \begin{array}{l} \dfrac{1}{7}x - \dfrac{2}{7} = 0\\ \dfrac{{ - 1}}{5}x + \dfrac{3}{5} = 0\\ \dfrac{1}{3}x + \dfrac{1}{3} = 0 \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} \dfrac{1}{7}x = \dfrac{2}{7}\\ - \dfrac{1}{5}x = - \dfrac{3}{5}\\ \dfrac{1}{3}x = - \dfrac{1}{3} \end{array} \right. \Leftrightarrow \left[ \begin{array}{l} x = 2\\ x = 3\\ x = - 1 \end{array} \right. \)
15: Tính
a) Ta có: \(\frac{3^6\cdot45^4-15^{13}\cdot5^{-9}}{27^4\cdot25^3+45^6}\)
\(=\frac{3^6\cdot3^4\cdot15^4-15^{13}\cdot\frac{1}{5^9}}{9^4\cdot3^4\cdot5^6+9^6\cdot5^6}\)
\(=\frac{3^6\cdot45^4-\frac{5^{13}\cdot3^{13}}{5^9}}{9^4\cdot5^6\left(3^4+9^2\right)}\)
\(=\frac{45^4\cdot3^6-5^4\cdot3^{13}}{45^4\cdot5^2\cdot2\cdot9^2}\)
\(=\frac{5^4\cdot3^6\left(9^4-3^7\right)}{5^2\cdot3^4\cdot45^4\cdot2}\)
\(=\frac{5^2\cdot3^2\cdot\left(3^8-3^7\right)}{45^4\cdot2}\)
\(=\frac{5^2\cdot3^9\cdot\left(3-1\right)}{5^4\cdot3^8\cdot2}\)
\(=\frac{1}{5^2}\cdot3\)
\(=\frac{3}{25}\)
cái này mk làm r!!!