Question

If the 50th and 51st terms of an arithmetic sequence are 140 and 142, find the 1st term

Answer 1

The first term is 42.

Explanation:

The common difference is 142 - 140 = 2 so we have

50th term = a1 + 2(50 -1) = 140 where a1 is the first term

a1 + 98 = 140

a1 = 140 - 98 = 42.