`a, s(3)=-2.3^3+24.3^2+9.3-3=186`

`→Đ`

`b, \text(v)=s'(t)=-2.3t^2+24.2t+9=-6t^2+48t+9`

`→Đ`

`c, s' ' (t)=-12t+48`

`a(10)= s' ' (10)=-12.10+48=-72 ` `m // s^2<0`

`=>` vật cđ chậm dần

`→S`

`d, s'(t)=-6t^2+48t+9`

`\text(v)=-6t^2+48t+9=-6(t^2-2.4t+4^2-4^2)+9`

`\text(v)=-6(t-4)^2-6.(-4^2)+9=-6(t-4)^2+105≤105`

`=>\text(v)_(\text(max))=105 m // s`

`→Đ`

`- \text(Lamtoanbangcatinhmang) -`