JEE Mains · Maths · STD 11 - 8. sequence and series
If \(a _{1}(>0), a _{2}, a _{3}, a _{4}, a _{5}\) are in a G.P., \(a _{2}+ a _{4}=2 a _{3}+1\) and \(3 a _{2}+ a _{3}=2 a _{4}\), then \(a _{2}+ a _{4}+2 a _{5}\) is equal to
- A \(30\)
- B \(20\)
- C \(30\)
- D \(40\)
Answer & Solution
Correct Answer
(D) \(40\)
Step-by-step Solution
Detailed explanation
\(a _{1}>0, a _{2}, a _{3}, a _{4}, a _{5} \rightarrow G \cdot P .\) \(3 a _{2}+ a _{3}=2 a _{4}\) \(3 ar + ar ^{2}=2 ar ^{3}\) \(3+ r =2 r ^{2}\) \(2 r ^{2}- r -3=0\) \(r =-1\) and \(r =\frac{3}{2}\) \(a _{2}+ a _{4}=2 a _{3}+1\) \(ar + ar ^{3}=2 ar ^{2}+1\)…
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