Question

How and when middle most term formula (n+1/2)th term is used?

Answer 1

Given AP is 20,16,12.............[-176] Here a = 20, d = 16 – 20 = – 4 tn = –176 nth term of an AP is tn = a + (n – 1)d ⇒ –176 = 20 + (n – 1)(– 4) ⇒ –176 = 20 – 4n + 4 ⇒ –176 = 24 – 4n ⇒ –176 – 24 = –4n ⇒ –200 = – 4n ∴ n = 50 The middle terms are 25th and 26th terms t25 = 20 + (25 – 1)(– 4) = 20 – 96 = –76 t26 = 20 + (26 – 1)(– 4) = 20 – 100 = –80