$S=S_0+V_0t+\frac{1}{2}at^2$
$V_{śr} = \frac{\Delta S}{\Delta t}$
$V = \frac{ds}{dt} = S'(t) = V_0+at$
$a=\frac{dv}{dt}=V'(t) \lor a=\frac{V-V_0}{t}=\frac{\Delta V}{t}$