13 tháng 7 2021 lúc 14:21
a) Ta có: \(\sqrt{16x}=8\)
\(\Leftrightarrow16x=64\)
hay x=4
b) Ta có: \(\sqrt{4x}=\sqrt{5}\)
nên 4x=5
hay \(x=\dfrac{5}{4}\)
c) Ta có: \(\sqrt{9\left(x-1\right)}=21\)
\(\Leftrightarrow9\left(x-1\right)=441\)
\(\Leftrightarrow x-1=49\)
hay x=50
d) Ta có: \(\sqrt{4\left(1-x\right)^2}-6=0\)
\(\Leftrightarrow2\left|x-1\right|=6\)
\(\Leftrightarrow\left|x-1\right|=3\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1=3\\x-1=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-2\end{matrix}\right.\)
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