Câu 1
\(4x^2-4x=-1\)
\(4x^2-4x+1=0\)
\(\left(2x+1\right)^2=0\)
\(2x+1=0\)
\(2x=-1\)
\(x=-\dfrac{1}{2}\)
Câu 2
\(x^2+5x=0\)
\(\Leftrightarrow x\left(x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\)
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