How do you find the first term of the arithmetic sequence given Sn = 781, d = 3, n = 22?
The first term is
In this sequence we know the sum of 22 terms, the difference and we have to calculate the first term. We will use the formula for the sum of n terms:
In this formula we have all data except
When we substitute (2) to (1) we get:
Now we can substitute given data and calculate