We have:\(64x+16x^2-4x^3-x^4=0\)

\(\Leftrightarrow16x\left(x+4\right)-x^3\left(x+4\right)=0\)

\(\Leftrightarrow\left(16x-x^3\right)\left(x+4\right)=0\)

\(\Leftrightarrow x\left(x+4\right)\left(16-x^2\right)=0\)

\(\Leftrightarrow x\left(4-x\right)\left(x+4\right)^2=0\)

\(\Rightarrow\left[{}\begin{matrix}x=0\\4-x=0\\x+4=0\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x=0\\x=4\\x=-4\end{matrix}\right.\)

We have:64x+16x2−4x3−x4=0

⇔16x(x+4)−x3(x+4)=0

⇔(16x−x3)(x+4)=0

⇔x(x+4)(16−x2)=0

⇔x(4−x)(x+4)2=0

⇒⎡⎢⎣x=04−x=0x+4=0

⇒⎡⎢⎣x=0x=4x=−4