`a)` `3x^4-12x^3+12x^2=0`
`⇔3x^2(x^2-4x+4)=0`
`⇔3x^2(x-2)^2=0`
`⇔x^2(x-2)^2=0`
`⇔` \(\left[ \begin{array}{l}x^2=0\\(x-2)^2=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=0\\x=2\end{array} \right.\)
`text{ Vậy }` `x∈{0;2}`
`b)` `(2x^4-7x^3-7x^2-6x-2):(2x^2+x+1)`
`=\frac{2x^4-7x^3-7x^2-6x-2}{2x^2+x+1}`
`=\frac{2x^4+x^3-8x^3+x^2-4x^2-4x^2-4x-2x-2}{2x^2+x+1}`
`=\frac{x^2(2x^2+x+1)-4x(2x^2+x+1)-2(2x^2+x+1)}{2x^2+x+1}`
`=\frac{(2x^2+x+1)(x^2-4x-2)}{2x^2+x+1}`
`=x^2-4x-2`
