4.
已知等比数列\(\left\{ \mathbf{a}_{\mathbf{n}} \right\}\)的公比\(\mathbf{q}{ > }0\),其前\(\mathbf{n}\)项和为\(\mathbf{S}_{\mathbf{n}}\),若\(\mathbf{a}_{\mathbf{1}}\mathbf{{=}1}\),\(\mathbf{4}\mathbf{a}_{\mathbf{3}}\mathbf{{=}}\mathbf{a}_{\mathbf{2}}\mathbf{a}_{\mathbf{4}}\).
\((1)\)求公比\(\mathbf{q}\)和\(\mathbf{a}_{\mathbf{5}}\)的值;
\((2)\)求证:\(\dfrac{\mathbf{S}_{\mathbf{n}}}{\mathbf{a}_{\mathbf{n}}}\mathbf{{ < }}2\).