Answer:
(n-1) / 2
Step-by-step explanation:
We have that the sum has the form of:
Sn = n / 2 [2 * a + (n-1) * d]
we compute the terms of a and d
a = 1 - 1 / n
a = (n - 1) / n
, that is, the first term, in the case d is the subtraction between the second and the first term, thus:
d = 1 - 2 / n - (1 - 1 / n)
d = 1 - 2 / n - 1 + 1 / n
d = - 1 / n
now if replacing these values:
Sn = n / 2 * [2 * (n - 1) / n + (n-1) * (- 1 / n)
Sn = n / 2 * [2 * (n-1) - (n-1)] / n
Sn = 1/2 * (n-1)
Therefore, the value of that sum is (n-1) / 2
