\(x^2\left(x-5\right)-4\left(5-x\right)=0\)
\(\Leftrightarrow x^2\left(x-5\right)+4\left(x-5\right)=0\)
\(\Leftrightarrow\left(x^2+4\right)\left(x-5\right)=0\)
\(\Rightarrow x-5=0\) (vì \(x^2+4>0\forall x\))
\(\Leftrightarrow x=5\)
`x^2(x-5)-4(5-x)=0`
\(\Leftrightarrow x^2\left(x-5\right)+4\left(x-5\right)=0\\ \Leftrightarrow\left(x-5\right)\left(x^2+4\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x-5=0\\x^2+4=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=5\\x^2=-4\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=5\\x\in\varnothing\end{matrix}\right.\)
