`2x^3-4x^2-2x+4=0`
`<=>2x^2(x-2)-2(x-2)=0`
`<=>2(x-2)(x^2-1)=0`
`<=>(x-2)(x-1)(x+1)=0`
`<=>`$\left[\begin{matrix} x-2=0\\x+1=0\\ x-1=0\end{matrix}\right.$
`<=>`$\left[\begin{matrix} x=2\\x=-1\\ x=1\end{matrix}\right.$
`text{vậy}` `S={2;-1;1}`
`-----------------------`
`5x^2-4x+10xy-8`
`=(5x^2+10xy)-(4x+8)`
`=5x(x+2y)-4(x+2y)`
`=(x+2y)(5x-4)`
`----------------------`
`x^3+2x^2-9x-18=0`
`<=>x^2(x+2)-9(x+2)=0`
`<=>(x+2)(x^2-9)=0`
`<=>(x+2)(x-3)(x+3)=0`
`<=>`$\left[\begin{matrix} x+2=0\\x-3=0\\ x+3=0\end{matrix}\right.$
`<=>`$\left[\begin{matrix} x=-2\\x=3\\ x=-1\end{matrix}\right.$
`text{vậy}` `S={-2;3;-3}`
`----------------------`
`x^2y+xy^2-x-y`
`=xy(x+y)-(x+y)`
`=(x+y)(xy-1)`
`text{xin 5 sao và hay nhất nha}`
$#VUBUIBUI$