Use the arithmetic sequence nth term formula to solve the following problem:

The first, second, and the nth terms of an arithmetic sequence are 2, 6, and 58 respectively:

find the value of n

and For that value of n, what is the exact value of the sum of n terms.

1 answer

the common difference is ... 6 - 2

the change from 6 to 58 is ... 58 - 6

the number of terms from 6 to 58 is ... (58 - 6) / (6 - 2)
... add in the 1st two terms to find n

sum = (58 + 2) * (n / 2)