Answer:
The first term is 42.
Step-by-step 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.
Are you sure you've copied down the original problem exactly as given? i38 = 38i can't be simplified. Perhaps you meant i^38, which is a different matter.
Note that i^38 = i^32 * I^4 * I^2.
Note that i^0, i^4, i^8, etc., all equal 1. Therefore,
i^38 = (1)(1)i^2 = 1*(-1) = -1 (answer)