`#Sad`
`a,`
`3x(x-2)-x+2 = 0`
`⇔ 3x(x-2)-(x-2) = 0`
`⇔ (3x-1)(x-2) = 0`
`⇔` \(\left[ \begin{array}{l}3x-1=0\\x-2=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}3x=1\\x=2\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=\dfrac{1}{3}\\x=2\end{array} \right.\)
`\text{Vậy S=}` `{ 1/3; 2 }`
`b,`
`16x^2-9(x+1)^2 = 0`
`⇔ (4x)^2-[3. (x+1)]^2 = 0`
`⇔ [4x-(3x+3)][4x+(3x+3)] = 0`
`⇔ (x-3)(7x+3) = 0`
`⇔` \(\left[ \begin{array}{l}x-3=0\\7x+3 = 0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=3\\7x=-3\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=3\\x=\dfrac{-3}{7}\end{array} \right.\)
`\text{Vậy S=}` `{3; -3/7 }`
`c,`
`x^3-2x^2-x+2 = 0`
`⇔ x^2(x-2)-(x-2) = 0`
`⇔ (x^2-1)(x-2) = 0`
`⇔ (x-1)(x+1)(x-2) = 0 `
`⇔` \(\left[ \begin{array}{l}x-1=0\\x+1=0\\x-2=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=1\\x=-1\\x=2\end{array} \right.\)
`\text{Vậy S=}` `{ 1; -1; 2 }`
`d,`
`8x^3-50x = 0`
`⇔2x(4x^2-25) = 0`
`⇔ 2x(2x-5)(2x+5) = 0`
`⇔` \(\left[ \begin{array}{l}2x=0\\2x-5=0\\2x+5=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=0\\2x=5\\2x=-5\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=0\\x=\dfrac{5}{2}\\x=\dfrac{-5}{2}\end{array} \right.\)
`\text{Vậy S=}` `{ 0; 5/2; -5/2 }`
`e,`
`x^3+27+(x+3)(x-9) = 0`
`⇔ (x+3)(x^2-3x+9)+(x+3)(x-9) = 0`
`⇔ (x+3)(x^2-3x+9+x-9) = 0`
`⇔ (x+3)(x^2-2x) = 0`
`⇔ x(x-2)(x+3) = 0`
`⇔` \(\left[ \begin{array}{l}x=0\\x-2=0\\x+3=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=0\\x=2\\x=-3\end{array} \right.\)
`\text{Vậy S=}` `{ 0; 2; -3 }`
