TS EAMCET · Maths · Sequences and Series
If \(1.3 .5+3.5 .7+5.7 .9+\ldots\) to \(n\) terms \(=n(n+1) f(n)\), then \(f(2)=\)
- A \(12\)
- B \(42\)
- C \(18\)
- D \(20\)
Answer & Solution
Correct Answer
(D) \(20\)
Step-by-step Solution
Detailed explanation
\(\begin{aligned} & \text { } 1 \cdot 3 \cdot 5+3 \cdot 5 \cdot 7=2 \times(2+1) f(2) \\ & 120=6 f(2) \Rightarrow f(2)=20\end{aligned}\)
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