Final answer:
The formula sn = n/2 [2a + (n-1)d] is used to find the sum of an arithmetic series by substituting the values of n, a, and d.
Step-by-step explanation:
The formula sn = n/2 [2a + (n-1)d] is used to find the sum of an arithmetic series. Here is an explanation of the terms:
- n: the number of terms in the series
- a: the first term of the series
- d: the common difference between consecutive terms
To find the sum of the series, you substitute the values of n, a, and d into the formula. For example, if you have a series with n = 5, a = 1, and d = 2, the formula becomes s5 = 5/2 [2(1) + (5-1)(2)] = 5/2 [2 + 4(2)] = 5/2 [2 + 8] = 5/2(10) = 25.