La expresión a considerar es :
<img src="https://tex.z-dn.net/?f=x%28t%29%3D-2%5Ct%2B3%5C%2Ct%5E%7B2%7D-0.5%5C%2Ct%5E%7B3%7D" />
Luego recordando que :
<img src="https://tex.z-dn.net/?f=v%3D%5Cfrac%7Bdx%7D%7Bdt%7D%5C%5C%20a%3D%5Cfrac%7Bdv%7D%7Bdt%7D" />
Entonces :
<img src="https://tex.z-dn.net/?f=x%27%28t%29%3D-2%2B6t-1.5t%5E%7B2%7D%5C%5C%20x%27%27%28t%29%3D6-3.0t" />
La posición, velocidad y aceleración para <img src="https://tex.z-dn.net/?f=t%3D2%5C%2Cs" /> es :
<img src="https://tex.z-dn.net/?f=%20x%282%29%3D-4%2B12-4.0%3D12%5C%2Cm%5C%5C%20x%27%282%29%3D-2%2B12-2%3D12%5C%2Cm%2Fs%5C%5C%20x%27%27%282%29%3D6-6%3D0%5C%2Cm%2Fs%5E%7B2%7D" />
La velocidad y aceleración media es :
<img src="https://tex.z-dn.net/?f=x%27%286%29%3D-2%2B36-54%3D-20%5C%5C%20x%27%27%286%29%3D6-18%3D-12%5C%5C%20v_%7Bmed%7D%3D%5Cfrac%7Bx_%7Bf%7D-x_%7Bi%7D%7D%7Bt_%7Bi%7D-t_%7Bf%7D%7D%3D%5Cfrac%7B-12-12%7D%7B6-2%7D%3D%5Cfrac%7B-24%7D%7B4%7D%3D-6%5C%2Cm%2Fs%5C%5C%20a_%7Bmed%7D%3D%5Cfrac%7Bv_%7Bf%7D-v_%7Bi%7D%7D%7Bt_%7Bf%7D-t_%7Bi%7D%7D%3D%5Cfrac%7B-20-12%7D%7B6-2%7D%3D%5Cfrac%7B-32%7D%7B4%7D%3D-8%5C%2Cm%2Fs%5E%7B2%7D" />
Saludos.