Question

Please help! Consider the sequence {20, 17, 14, 11, 8, 5, 2...}.

Answer 1

c.) 38

Explanation:

`\sum\limits_(n=3)^6 a_n` means "summation of the all the elements starting from the 3rd element to the 6th element".

The 3rd element in the series is 14, and the 6th element is 5; we have to add these and all the elements between them together.

∴
`\sum\limits_(n=3)^6 a_n` = 14 + 11 + 8 + 5

= 38