Answer:
[tex]\huge \red {\bigg \{\frac{ - 5  +  \sqrt{10}}{3}, \:  \:   \frac{ - 5  -   \sqrt{10}}{3}\bigg \}}[/tex] 
Step-by-step explanation:
[tex]3 {x}^{2}  =  - 10x - 5 \\ 3 {x}^{2}  + 10x + 5 = 0 \\ equating \: it \: with \\ a {x}^{2}  + bx + c = 0 \\ a = 3 \:  \: b = 10 \:  \: c = 5 \\ now \: by \: quadratic \: formula \\ x =  \frac{ - b \pm \sqrt{ {b}^{2} - 4ac } }{2a}  \\ plug \: a = 3 \:  \: b = 10 \:  \: c = 5  \: in \: the \\ above \: formula \\ x =  \frac{ - 10 \pm \sqrt{ {(10)}^{2}  - 4(3)(5) }}{2 \times 3} \\ x =  \frac{ - 10 \pm \sqrt{ {100} - 60}}{6} \\ x =  \frac{ - 10 \pm \sqrt{40}}{6} \\ x =  \frac{ - 10 \pm2 \sqrt{10}}{6} \\ x =  \frac{ 2(- 5 \pm \sqrt{10})}{6} \\ x =  \frac{ - 5 \pm \sqrt{10}}{3} \\ x =    \purple{ \bold{\bigg \{\frac{ - 5  +  \sqrt{10}}{3}, \:  \:   \frac{ - 5  -   \sqrt{10}}{3}\bigg \}}}[/tex]