Verified answer

[tex]\displaystyle\bf\\S(t)=\frac{2}{3} t^{3} -2t^{2} +6t\\\\\\V(t)=S'(t)=\frac{2}{3} \cdot(t^{3} )'-2\cdot(t^{2} )'+6\cdot t'=\frac{2}{3} \cdot3t^{2}-2\cdot 2t+6\cdot 1=\\\\=2t^{2} -4t+6\\\\V(t)=36\\\\36=2t^{2} -4t+6\\\\2t^{2} -4t-30=0\\\\t^{2}-2t-15=0\\\\Teorema \ Vieta:\\\\t_{1} =5\\\\t_{2} =-3-neyd[/tex]

Ответ : через 5 секунд