`x^8+36x^4=0`
`<=>x^4(x^4+36)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x^4=0\\x^4+36=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x^4=-36\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x\in\varnothing\end{matrix}\right.\)
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`(x-5)^3 -x+5=0`
`<=> (x-5)^3 -(x-5)=0`
`<=> (x-5) [(x-5)^2 -1]=0`
`<=> (x-5)(x-5-1)(x-5+1)=0`
`<=>(x-5)(x-6)(x-4)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-5=0\\x-6=0\\x-4=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=5\\x=6\\x=4\end{matrix}\right.\)
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`5(x-2)-x^2+4=0`
`<=>5(x-2)-(x^2-4)=0`
`<=>5(x-2)-(x-2)(x+2)=0`
`<=>(x-2)(5-x-2)=0`
`<=>(x-2)(-x-3)=0`
\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\-x-3=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)
