1.

The fourth term of a G.P. is 27, and the 7th term is 729, find the G.P.

Answer»

Tn = arn-1 

a =a, r =?, Tn = 27 n = 4 

a =a, r =?, Tn = 729 n = 7 

∴ 27 = a.r4-1 

⇒ 27 =a.r3…(1) 

∴ 729 = a.r7-1 

⇒ 729 = a.r6…(2) 

Divide (2) by (1) we get 

\(\frac{729}{27}\)  = \(\frac{ar^6}{ar^3}\)

⇒ r3 = 27 

⇒ r = 3 

Substituting r in 1 we get 

a = 1 

∴ GP = 1,3,9…



Discussion

No Comment Found