Find the fourth term from the end in an A.P. – 11, – 8, – 5, . . ., 49.

First term from end a = 49
t_n = – 11
t_{n – 1} = – 8
Common difference d = t_n – t_{n – 1}
= – 11 – ( – 8)
= – 11 + 8
= – 3
Now, by using n^th term of an A.P. formula
t_n = a + (n – 1) d
where n = no. of terms
a = first term
d = common difference
t_n = n^th terms
number of terms n = 4
⇒ t₄ = 49 + (4 – 1) × ( – 3)
⇒ t₄ = 49 + 3 × ( – 3)
⇒ t₄ = 49 – 9 = 40