Đáp án:
3B. d. x=5
Giải thích các bước giải:
\(\begin{array}{l}
3A\\
a.\left( {\dfrac{8}{5} - \dfrac{4}{3}} \right)x = - \dfrac{5}{{16}}.\dfrac{7}{5}\\
\to \dfrac{4}{{15}}x = - \dfrac{7}{{16}}\\
\to x = - \dfrac{{105}}{{64}}\\
c.\dfrac{1}{2} - \dfrac{4}{7}x = \sqrt[3]{{ - \dfrac{8}{{343}}}}\\
\to \dfrac{1}{2} - \dfrac{4}{7}x = - \dfrac{2}{7}\\
\to \dfrac{4}{7}x = \dfrac{1}{2} + \dfrac{2}{7}\\
\to \dfrac{4}{7}x = \dfrac{{11}}{{14}}\\
\to x = \dfrac{{11}}{8}\\
b.\dfrac{2}{3}x - \dfrac{1}{5} = \sqrt {\dfrac{4}{9}} \\
\to \dfrac{2}{3}x - \dfrac{1}{5} = \dfrac{2}{3}\\
\to \dfrac{2}{3}x = \dfrac{{13}}{{15}}\\
\to x = \dfrac{{13}}{{10}}\\
d{.7.3^x}.\dfrac{1}{3} - {3^2}{.3^x} = - 540\\
\to \left( {\dfrac{7}{3} - 9} \right){3^x} = - 540\\
\to - \dfrac{{20}}{3}{.3^x} = - 540\\
\to {3^x} = 81\\
\to {3^x} = {3^4}\\
\to x = 4\\
3B\\
a.\dfrac{2}{3}x - \dfrac{1}{2}x = - \dfrac{7}{{12}}.\dfrac{7}{5}\\
\to \dfrac{1}{6}x = - \dfrac{{49}}{{60}}\\
\to x = - \dfrac{{49}}{{10}}\\
c.\dfrac{{17}}{4} - \dfrac{4}{5}x = \sqrt[3]{{ - 125}}\\
\to \dfrac{{17}}{4} - \dfrac{4}{5}x = - 5\\
\to \dfrac{4}{5}x = \dfrac{{17}}{4} + 5\\
\to x = \dfrac{{185}}{{16}}\\
b.\dfrac{1}{5} - \dfrac{3}{2}x = \dfrac{3}{2}\\
\to \dfrac{3}{2}x = \dfrac{1}{5} - \dfrac{3}{2}\\
\to x = - \dfrac{{13}}{{15}}\\
d{.2^x} + {2^x}{.2^4} = 544\\
\to \left( {16 + 1} \right){2^x} = 544\\
\to {2^x} = 32\\
\to {2^x} = {2^5}\\
\to x = 5
\end{array}\)
