[填空题]
The first term and tvj2nr6 ee)lkvyckf4 i2 *gp4i )w+(vhh:d(cvv8 b d;itl1e(sc +hrl0xe common ratio of a geometric series are denoted, respectively, by e8br;0 dc citlv1 hlds(v( +:x$u_{1}$ 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 =
