The first term of a G.P. is 1. The sum of the third term and fifth term is 90. Find the common ratio of G.P.
Let a and r be the first term and the common ratio of the G.P. respectively.
∴ a = 1
a3 = ar2 = r2
a5 = ar4 = r4
∴ r2 + r4 = 90
⇒ r4 + r2 – 90 = 0
Concept: Geometric Progression (G. P.)
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