a) tìm x biết 3x^4-12x^3+12x^2=0 b làm tính chia (2x^4-7x^3-7x^2-6x-2):(2x^2+x+1)

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1. `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`

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