Giải
Tìm x:
a)\(\left(x-2\right)^2=1\Leftrightarrow\left(x-2\right)^2=1^2.\)
\(\Rightarrow\orbr{\begin{cases}x-2=1\Rightarrow x=1+2=3\\x-2=-1\Rightarrow x=-1+2=1\end{cases}}\)
=> Vậy \(x=\orbr{\begin{cases}3\\1\end{cases}}\)
b) \(\left(2x-1\right)^3=-8\Leftrightarrow\left(2x-1\right)^3=\left(-2\right)^3\)
\(\Rightarrow\left(2x-1\right)=-2\Rightarrow2x=-2+1=-1\)
\(\Rightarrow x=-1:2=-\frac{1}{2}\)
Vậy \(x=-\frac{1}{2}\)
c) \(\left(x+\frac{1}{2}\right)^2=\frac{1}{16}\Leftrightarrow\left(x+\frac{1}{2}\right)^2=\orbr{\begin{cases}\left(-\frac{1}{4}\right)^2\\\left(\frac{1}{4}\right)^2\end{cases}}\)
\(\Rightarrow\left(x+\frac{1}{2}\right)=\orbr{\begin{cases}-\frac{1}{4}\\\frac{1}{4}\end{cases}}\Rightarrow\orbr{\begin{cases}x+\frac{1}{2}=-\frac{1}{4}\Rightarrow x=-\frac{1}{4}-\frac{1}{2}=-\frac{3}{4}\\x+\frac{1}{2}=\frac{1}{4}\Rightarrow x=\frac{1}{4}-\frac{1}{2}=-\frac{1}{4}\end{cases}}\)
Vậy   \(x=-\frac{3}{4};-\frac{1}{4}\)
 

BT2:

Giải
a) \(9.3^3.\frac{1}{81}.3^2=3^2.3^3.\left(\frac{1}{3}\right)^4.3^2=\left(3^2.3^3.3^2\right).\left(\frac{1}{3}\right)^4\)
\(=3^{2+3+2}.\left(\frac{1}{3}\right)^4=3^7.\left(\frac{1}{3}\right)^4=\frac{3^7.1^4}{1.3^4}=3^3\)
b) \(4.2^5:\left(2^3.\frac{1}{16}\right)=2^2.2^5:\left(2^3.\left(\frac{1}{2}\right)^4\right)=2^{2+5}:\left(\frac{2^3.1^4}{2^4}\right)\)
\(=2^7:\left(\frac{1}{2}\right)=2^7.\frac{2}{1}=2^8\)
c) Chị đang nghĩ...

64

\(^{64^1=8^2=-8^2=4^3=2^6}\)

\(\frac{9.3^3.1}{81.3^2}=\frac{3^5}{3^6}=\frac{1}{3}=\sqrt{\frac{1}{9}}\)

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