(Solved): Express the sum in closed form (without using a summation symbol and without using an ellipsis ... ...

Express the sum in closed form (without using a summation symbol and without using an ellipsis ...). \[ \sum_{r=0}^{n}\left(\begin{array}{l} n \\ r \end{array}\right) x^{7 r} \] Express the sum in closed form (without using a summation symbol and without using an ellipsis ...). \[ \sum_{k=0}^{n}\left(\begin{array}{l} n \\ k \end{array}\right) \frac{1}{6^{k}} \]