a. \(\left(2x-1\right)^2-\left(4x^2-1\right)=0\Leftrightarrow\left(2x-1\right)^2-\left[\left(2x\right)^2-1^2\right]=0\Leftrightarrow\left(2x-1\right)^2-\left(2x-1\right)\left(2x+1\right)=0\Leftrightarrow\left(2x-1\right)\left(2x-1-2x-1\right)=0\Leftrightarrow-2\left(2x-1\right)=0\Leftrightarrow2x-1=0\Leftrightarrow2x=1\Leftrightarrow x=\dfrac{1}{2}\)
Vay \(x=\dfrac{1}{2}\)
b. \(x^2\left(x^2+4\right)-x^2-4=0\Leftrightarrow x^2\left(x^2+4\right)-\left(x^2+4\right)=0\Leftrightarrow\left(x^2+4\right)\left(x^2-1\right)=0\Leftrightarrow\left[{}\begin{matrix}x^2+4=0\\x^2-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x^2=-4\\x^2=1\end{matrix}\right.\Leftrightarrow x=\pm1\)
\(x^2=-4\) bị loại vì \(x^2\ge0\)
Vay \(x=\pm1\)