[填空题]
The first term and the co7y zv6r9mopn0 mmon ratio of a geometric series aret/dvh;ebiwbil(-y+9 3t . gc /lvkxm 2 denoted, respectivmvb9 bv l( -;yl2hi t/iwk+cxd e3./gtely, by $u_{1}$ and r , where $u_{1}$, $r \in \mathbb{Q}$ . Given that the fourth term is 64 and the sum to infinity is 625 , find the value of $u_{1}$ and the value of r .$u_{1}$ = r =
