Đáp án:
$\begin{array}{l}
6){\left( {\dfrac{{ - 3}}{2}} \right)^2} - \dfrac{5}{4} = \dfrac{9}{4} - \dfrac{5}{4} = \dfrac{4}{4} = 1\\
7){\left( {\dfrac{{ - 2}}{3}} \right)^4}:{\left( {\dfrac{{ - 2}}{3}} \right)^x} = 1\\
\Leftrightarrow {\left( {\dfrac{{ - 2}}{3}} \right)^{4 - x}} = 1\\
\Leftrightarrow 4 - x = 0\\
\Leftrightarrow x = 4\\
Vậy\,x = 4\\
8)5{x^2} - {4.2^2} = 29\\
\Leftrightarrow 5{x^2} = 29 + 4.4\\
\Leftrightarrow 5{x^2} = 45\\
\Leftrightarrow {x^2} = 9\\
\Leftrightarrow x = 3;x = - 3\\
Vậy\,x = 3;x = - 3\\
9){4^4}:{4^2} - 3{x^3} = 40\\
\Leftrightarrow {4^2} - 3{x^3} = 40\\
\Leftrightarrow 3{x^3} = - 24\\
\Leftrightarrow {x^3} = - 8\\
\Leftrightarrow x = - 2\\
Vậy\,x = - 2\\
10){\left( {x - 2} \right)^3} - 27 = - 35\\
\Leftrightarrow {\left( {x - 2} \right)^3} = - 8\\
\Leftrightarrow x - 2 = - 2\\
\Leftrightarrow x = 0\\
Vậy\,x = 0\\
11){3^{x + 2}} - {3^x} = 72\\
\Leftrightarrow {3^x}\left( {{3^2} - 1} \right) = 72\\
\Leftrightarrow {3^x} = 9\\
\Leftrightarrow x = 2\\
Vậy\,x = 2\\
12){4^{x + 1}} - {3.4^x} = 16\\
\Leftrightarrow {4^x}\left( {{4^1} - 3} \right) = 16\\
\Leftrightarrow {4^x} = 16\\
\Leftrightarrow x = 2\\
Vậy\,x = 2
\end{array}$
