1,
\(a,\left(x+2\right)^2-4=0\)
\(\Leftrightarrow\left(x+2+2\right)\left(x+2-2\right)=0\)
\(\Leftrightarrow x\left(x+4\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+4=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-4\end{matrix}\right.\)
Vậy \(S=\left\{0;-4\right\}\)
\(b,\left|x\right|=3x+5\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+5=x\\3x+5=-x\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{5}{2}\\x=-\dfrac{5}{4}\end{matrix}\right.\)
Vậy \(S=\left\{-\dfrac{5}{2};-\dfrac{5}{4}\right\}\)
2
\(2x-7< 5x+1\)
\(\Leftrightarrow2x-5x< 1+7\)
\(\Leftrightarrow-3x< 8\)
\(\Leftrightarrow x>-\dfrac{8}{3}\)
Vậy \(S=\left\{x\left|x>-\dfrac{8}{3}\right|\right\}\)
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