`6t^2-5t-10=0`
`<=>t^2-5/6t-5/3=0`
`<=>(t-5/12)^2-265/144=0`
`<=>(t-5/12-\frac{\sqrt{265}}{12})(t-5/12+\frac{\sqrt{265}}{12})=0`
`<=>`\(\left[ \begin{array}{l}t-\dfrac{5}{12}-\dfrac{\sqrt{265}}{12}=0\\t-\dfrac{5}{12}+\dfrac{\sqrt{265}}{12}=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}t=\dfrac{\sqrt{265}+5}{12}\\t=-\dfrac{\sqrt{265}+5}{12}\end{array} \right.\)
Vậy `S={\frac{\sqrt{265}+5}{12};-\frac{\sqrt{265}+5}{12}}`
