Question

Find 14th term of an A. P. Whose 5th term is 25and 8th term is 64.

Answer 1

nth Term of A.P is given by = a+(n-1)d
Given 5th Term = 25
=> 25= a+ 4d...(1)
Given 8th Term = 64
=> 64= a+ 7d...(2)

(2) - (1) => 64 -25 = 3d
39 =3d
d=13

subtituting d in (1) we get
=> 25= a+ 4*13
a = -27

Therefore nth term = -27 + 13(n-1)
14th Term of AP = -27 + 13 x 13
= 142