Solution 2.1.13.1.

1. \(\d\sum_{k=1}^n 2k\text{.}\)

2. \(\d\sum_{k=1}^{107} (1 + 4(k-1))\text{.}\)

3. \(\d\sum_{k=1}^{50} \frac{1}{k}\text{.}\)

4. \(\d\prod_{k=1}^n 2k\text{.}\)

5. \(\d\prod_{k=1}^{100} \frac{k}{k+1}\text{.}\)