[tex] v_m=\frac{x(4)-x(0)}{4-0}=\frac{9-1}{4}=2ms^{-1}. [/tex]
[tex] v(t)=x'(t)=(2t-2)ms^{-1}[/tex]
[tex]v(1)=0ms^{-1}. [/tex]
[tex] a(t)=v'(t)=2ms^{-2}. [/tex]
