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