\(7x\left(16x^2-1\right)=0\)
\(\Leftrightarrow7x\left(4x-1\right)\left(4x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{4}\\x=-\dfrac{1}{4}\end{matrix}\right.\)
\(\Rightarrow7x\left(4x-1\right)\left(4x+1\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{4}\\x=-\dfrac{1}{4}\end{matrix}\right.\)