Question

Use sigma notation to represent the sum of the first eight terms of the following sequence: 4, 7, 10, …

Answer 1

`\displaystyle \boxed{ \sum_(k=1)^(8) (1+3k) }`

Explanation:

Hello,

We are looking for something like

`\displaystyle \sum_(k=1)^(8) u_k`

where

`u_1=4\\ \\u_2=7 \\ \\u_3 =10 \\ \\u_k=1+3k`

So,

`\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* (9*8)/(2)\\ \\=8+108=116`

Thanks