The first three terms of an A.P. respectively are 3y – 1, 3y + 5 and 5y + 1. Then, y equals

Answer: Option C

2 (3y + 5) = 3y – 1 + 5y + 1
(If a, b, c are in A.P., b – a = c – b ⇒ 2b = a + c)
⇒ 6y + 10 = 8y
⇒ 10 = 2y
⇒ y = 5