Đáp án:
c. x=-1
Giải thích các bước giải:
\(\begin{array}{l}
a{.5^x}{.5^6} = {5^4}\\
\to {5^x} = \dfrac{{{5^4}}}{{{5^6}}}\\
\to {5^x} = \dfrac{1}{{{5^2}}}\\
\to {5^x} = {5^{ - 2}}\\
\to x = - 2\\
b.{\left( {\dfrac{{12}}{{25}}} \right)^x} = \dfrac{9}{{25}} - \dfrac{{81}}{{625}}\\
\to {\left( {\dfrac{{12}}{{25}}} \right)^x} = \dfrac{{144}}{{625}}\\
\to {\left( {\dfrac{{12}}{{25}}} \right)^x} = {\left( {\dfrac{{12}}{{25}}} \right)^2}\\
\to x = 2\\
c.{\left( { - \dfrac{3}{4}} \right)^{3x - 1}} = \dfrac{{256}}{{81}}\\
\to {\left( { - \dfrac{3}{4}} \right)^{3x}}.{\left( { - \dfrac{3}{4}} \right)^{ - 1}} = \dfrac{{256}}{{81}}\\
\to {\left( { - \dfrac{3}{4}} \right)^{3x}} = - \dfrac{{64}}{{27}}\\
\to {\left( { - \dfrac{3}{4}} \right)^{3x}} = {\left( { - \dfrac{4}{3}} \right)^3}\\
\to {\left( { - \dfrac{3}{4}} \right)^{3x}} = {\left( { - \dfrac{3}{4}} \right)^{ - 3}}\\
\to 3x = - 3\\
\to x = - 1
\end{array}\)
