3. Find the common difference d , giving your answer as an integer.
Let $S_{6}$ be the sum of the first 6 terms of the arithmetic sequence.
4. Show that $S_{6}=6$ $\log _{3} x-15$ .$a \log _{b} x-c$ a = b = c =
5. Given that $S_{6}$ is equal to one third of the sum of the infinite geometric sequence, find x , giving your answer in the form $a^{p}$ where a, $p \in \mathbb{Z}$ .$a^b$a = b =