a) 3x\(^2\)+8x+4=0
\(\Leftrightarrow3x^2+6x+2x+4=0\)
⇔ x( 3x + 2 ) + 2 ( 3x + 2 ) = 0
⇔ ( x + 2 ) ( 3x + 2 ) = 0
\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\3x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\frac{-2}{3}\end{matrix}\right.\)
b) 4x\(^2\)-4x-3=0
\(\Leftrightarrow4x^2-6x+2x-3=0\)
⇔ 2x( 2x + 1 ) - 3( 2x + 1 ) = 0
⇔ ( 2x - 3 ) ( 2x + 1 ) = 0
\(\Leftrightarrow\left[{}\begin{matrix}2x-3=0\\2x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{3}{2}\\x=\frac{-1}{2}\end{matrix}\right.\)
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