[填空题]
The first term and the common rgx8;d lb+ 0y lbzs-w+jajyzu wh/4j eq*v4*z.1dj4ty x t.fgw7tio of a geometric series are denoted, respectiveth14yjdj.e*/uz*w4z q w4vfxyg7j .tly, 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 =
