Question

The 5th term of an AP is 9 and the 8th is 27 find the 13th term

Answer 1

Tn = a + (n-1) d

T5 = a + 4 d = 9
T8 = a + 7 d = 27
----------------------- subtract
-3 d = -18
d = 6
a + 4*6 = 9
a = -15
T13 = -15 + 12*6 = -15 + 72 = 57