\(9x^2+6x-8=0\)
\(\Leftrightarrow9x^2-6x+12x-8=0\)
\(\Leftrightarrow3x\left(3x-2\right)+4\left(3x-2\right)=0\)
\(\Leftrightarrow\left(3x+4\right)\left(3x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}3x+4=0\\3x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-4}{3}\\x=\dfrac{2}{3}\end{matrix}\right.\)
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