Đáp án: + Giải thích các bước giải:
`(3x^2-1)/x + (5x)/(3x^2-x-1) = 119/18`
`⇔ 18(3x^2-1)(3x^2-x-1)+90x^2=119x(3x^2-x-1)`
`⇔ 162x^4 - 54x^3 - 18x^2 + 137x + 18 = 357x^3 - 119x^2`
`⇔ 162x^4 - 411x^3 + 101x^2 + 137x + 18 = 0`
`⇔ (x-2)(6x+1)(27x^2-19x-9)=0`
`⇔`\(\left[ \begin{array}{l}x-2=0\\6x+1=0\\27x^2-19x-9=0\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}x=2\\x=-\dfrac{1}{6}\\x=\dfrac{19\pm\sqrt{1333}}{54}\end{array} \right.\)
Vậy `S = {2,-1/6,(19\pm\sqrt{1333})/54}`
