# Greatest lower bound/least upper bound in Q

I have the following question:

Let $n\in\mathbb{Z}^{+}$ st. $n$ is not a perfect square. Let $A=\{x\in\mathbb{Q}|x^{2}<n\}$. Show that $A$ is bounded in $\mathbb{Q}$ but has neither a greatest lower bound or a least upper bound in $\mathbb{Q}$.

To show that $A$ is bounded in $\mathbb{Q}$ I have to show that it has a infimum and a supremum in $\mathbb{Q}$, right? Not sure where to start...