The sum of the first four terms of a linear sequence is 26 and that of the next four terms is 74.
Find the value of:
The first term
The common difference
using sum(n) = (n/2)(2a + (n-1)d )
26 = (4/2)(2a + 3d) ====> 2a + 3d = 13
sum(8) = 4(2a + 7d) = 26 + 74 ====> 2a + 7d = 25
subtract them:
4d = 12
d = 3 , then a = 2