Question

The 8th term of an ap is 17 and the 19 term is 39 find the 25 tetm

Answer 1

8th term = a+7d = 17 ----(1)

19th term = a+18d = 39 -----(2)

solving (1) and (2)

a+7d = 17

a+18d = 39

(-)   (-)     (-)

---------------------

-11d= -22

d = 2

sub d=2 in 1-

a+7*2 = 17

a = 3

a_25 = a+(25-1) d

a_25 = 3+24*2

hence, a_25 = 51