Question

For an A.P., t₄ = 12 and its common difference d = –10, then find t_n.

Answer 1

t₄ = 12, d = –10   ...[Given]

Since t_n = a + (n – 1)d,

t₄ = a + (4 – 1)(–10)

∴ 12 = a + 3(–10)

∴ 12 = a – 30

∴ a = 42

t_n = a + (n – 1)d

= 42 + (n – 1)(–10)

= 42 – 10n + 10

= 52 – 10n