`a) x^3-16x=0`
`<=> x(x^2-16)=0`
`<=> x(x-4)(x+4)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\x-4=0\\x+4=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=4\\x=-4\end{array} \right.\)
`b) 2x^2-8x=0`
`<=> 2x(x-4)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\x-4=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=4\end{array} \right.\)
`c) x^4-2x^3+10x^2=20x`
`<=>x^3(x-2)+10x^2-20x=0`
`<=> x^3(x-2)+10x(x-2)=0`
`<=> (x-2)(x^3+10x)=0`
`<=> x(x-2)(x^2+10)=0`
do `x^2+10>=10` với `∀x`
`=>`\(\left[ \begin{array}{l}x=0\\x-2=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
`d) (x-1)^2=(x+3)^2`
`<=>(x-1)^2-(x+3)^2=0`
`<=> (x-1-x-3)(x-1+x+3)=0`
`<=> -4(2x+2)=0`
`<=> x+1=0`
`<=> x=-1`
