Question

What is the sum of a 58–term arithmetic sequence where the first term is 6 and the last term is 405? please helpp.

Answer 1

the sum of an arythmetic sequence for first term, a1 and last term, an and up to the term, n is

`s_n= (n(a1+an))/(2)`
n=58
a1=6
a58=405


`s_(58)= (58(6+405))/(2)`

`s_(58)= (58(411))/(2)`

`s_(58)= (23838)/(2)`

`s_(58)= 11919`


sum is 11,919