[tex]\displaystyle\bf\\X(t)=t^{2} +\frac{1}{t+1} \\\\\\V(t)=X'(t)=\Big(t^{2} \Big)'+\Big(\frac{1}{t+1} \Big)'=2t-\frac{1}{(t+1)^{2} } \\\\\\V(1)=2\cdot 1-\frac{1}{(1+1)^{2} } =2-\frac{1}{4} =1,75\\\\\\a(t)=V'(t)=2\cdot t'-\Big(\frac{1}{(t+1)^{2} } \Big)'=2+\frac{2}{(t+1)^{3} } \\\\\\a(1)=2+\frac{2}{(1+1)^{3} } =2+\frac{1}{4} =2,25[/tex]