$\displaystyle a_{n}=\frac{n}{n+1}$

is bounded below by $\displaystyle \frac{1}{2}$

and above by $\displaystyle 1$

here they mean the greatest lower bound and least upper bound..

so I don't understand how u could find these bounds by simply being given

$\displaystyle a_{n}=\frac{n}{n+1}$

can some one please explain to me how this work?