Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
b,\\
{\left( {x - \dfrac{2}{3}} \right)^3} = {\left( {\dfrac{2}{3}} \right)^6}\\
\Leftrightarrow {\left( {x - \dfrac{2}{3}} \right)^3} = {\left[ {{{\left( {\dfrac{2}{3}} \right)}^2}} \right]^3}\\
\Leftrightarrow {\left( {x - \dfrac{2}{3}} \right)^3} = {\left( {\dfrac{4}{9}} \right)^3}\\
\Leftrightarrow x - \dfrac{2}{3} = \dfrac{4}{9}\\
\Leftrightarrow x = \dfrac{4}{9} + \dfrac{2}{3}\\
\Leftrightarrow x = \dfrac{{10}}{9}\\
c,\\
172{x^2} - {7^9}:{98^3} = {2^{ - 3}}\\
\Leftrightarrow 172{x^2} - \dfrac{{{7^9}}}{{{{\left( {{7^2}.2} \right)}^3}}} = \dfrac{1}{8}\\
\Leftrightarrow 172{x^2} - \dfrac{{{7^9}}}{{{7^6}{{.2}^3}}} = \dfrac{1}{8}\\
\Leftrightarrow 172{x^2} - \dfrac{{{7^3}}}{8} = \dfrac{1}{8}\\
\Leftrightarrow 172{x^2} = 43\\
\Leftrightarrow {x^2} = \dfrac{1}{4}\\
\Leftrightarrow \left[ \begin{array}{l}
x = \dfrac{1}{2}\\
x = - \dfrac{1}{2}
\end{array} \right.\\
d,\\
{\left( {x - \dfrac{1}{2}} \right)^2} = \dfrac{1}{4}\\
\Leftrightarrow \left[ \begin{array}{l}
x - \dfrac{1}{2} = \dfrac{1}{2}\\
x - \dfrac{1}{2} = - \dfrac{1}{2}
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
x = 1\\
x = 0
\end{array} \right.\\
e,\\
\left( {\dfrac{{21}}{5} - 0,4} \right):x = {\left( {\dfrac{1}{2}} \right)^2} - 5,95\\
\Leftrightarrow \left( {\dfrac{{21}}{5} - \dfrac{2}{5}} \right):x = \dfrac{1}{4} - \dfrac{{119}}{{20}}\\
\Leftrightarrow \dfrac{{19}}{5}:x = - \dfrac{{57}}{{10}}\\
\Leftrightarrow x = \dfrac{{19}}{5}:\left( { - \dfrac{{57}}{{10}}} \right)\\
\Leftrightarrow x = - \dfrac{2}{3}
\end{array}\)
Em viết rõ đề câu a ra nhé!
