a/ \(\dfrac{\left(-3\right)^x}{81}=-27\)
\(\Leftrightarrow\left(-3\right)^x=\left(-27\right).81\)
\(\Leftrightarrow\left(-3\right)^x=-2187\)
\(\Leftrightarrow\left(-3\right)^x=\left(-3\right)^7\)
\(\Leftrightarrow x=7\)
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b/ \(2^{x-1}=16\)
\(\Leftrightarrow2^{x-1}=2^4\)
\(\Leftrightarrow x-1=4\)
\(\Leftrightarrow x=5\)
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c/ \(\left(x-1\right)^2=25\)
\(\Leftrightarrow\left(x-1\right)^2=5^2=\left(-5\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=5\\x-1=-5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-4\end{matrix}\right.\)
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d/ \(0,2-\left|4,2-2x\right|=0\)
\(\Leftrightarrow\left|4,2-2x\right|=0,2\)
\(\Leftrightarrow\left[{}\begin{matrix}4,2-2x=0,2\\4,2-2x=-0,2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=4\\2x=4,4\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=2,2\end{matrix}\right.\)
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e, \(1\dfrac{2}{3}:\dfrac{x}{4}=6:0,3\)
\(\Leftrightarrow\dfrac{5}{3}.\dfrac{4}{x}=20\)
\(\Leftrightarrow3x=1\)
\(\Leftrightarrow x=\dfrac{1}{3}\)
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