[填空题]
The first term and the common raa8(h aun71 pmgs-u mx7t )u if,5g*yb /sq-u 7xu5;x p0zsfngzuio of a geometric series are denoted, respectivelx fz *f/uz7gxqsp0s55u gni, uy-b);u y, 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 =
