\(a,2x-1-3x\left(2x-1\right)=0\)
\(\Leftrightarrow2x-1-6x^2+3x=0\)
\(\Leftrightarrow5x-1-6x^2=0\)
\(\Leftrightarrow6x^2-5x+1=0\)
\(\Leftrightarrow6x^2-2x-3x+1=0\)
\(\Leftrightarrow2x\left(3x-1\right)-\left(3x-1\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(3x-1\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2x-1=0\\3x-1=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}2x=1\\3x=1\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{1}{3}\end{cases}}\)
\(b,2x^2+4x=0\)
\(\Leftrightarrow2x\left(x+4\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}2x=0\\x+4=0\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\x=-4\end{cases}}\)
