Answer:
[tex]\displaystyle \boxed{ \sum_{k=1}^{8} (1+3k) }[/tex]
Step-by-step explanation:
Hello,
We are looking for something like
[tex]\displaystyle \sum_{k=1}^{8} u_k[/tex]
where
[tex]u_1=4\\ \\u_2=7 \\ \\u_3 =10 \\ \\u_k=1+3k[/tex]
So,
[tex]\displaystyle \sum_{k=1}^{8} u_k=\sum_{k=1}^{8} (1+3k)\\\\=\sum_{k=1}^{8} (1)+3\sum_{k=1}^{8} (k)\\\\=8+3\times \dfrac{9*8}{2}\\ \\=8+108=116[/tex]
Thanks
