s(t)=t^3-9t^2+28t
0=t^3-9t^2+28t
t^3-9t^2+28t=0
t*(t^2-9t+28)=0
t1=0
t^2-9t+28=0
t2=t∈R
> 0 - наименьшая
s(t)=t^3-9t^2+28t
0=t^3-9t^2+28t
t^3-9t^2+28t=0
t*(t^2-9t+28)=0
t1=0
t^2-9t+28=0
t2=t∈R
> 0 - наименьшая