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AP EAMCET · Maths · Functions

If \(1.3 .5+3.5 .7+5.7 .9+\ldots n\) terms \(=n(n+1) f(n)-3 n\), then \(f(1)=\)

  1. A 9
  2. B 11
  3. C 12
  4. D 8
Verified Solution

Answer & Solution

Correct Answer

(A) 9

Step-by-step Solution

Detailed explanation

\(1 \cdot 3 \cdot 5+3 \cdot 5 \cdot 7+5 \cdot 7 \cdot 9+\ldots . n\) terms \(\begin{aligned} & T_n=(2 n-1)(2 n+1)(2 n+3)=8 n^3+12 n^2-2 n-3 \\ & S_n=\Sigma T_n=8 \Sigma n^3+12 \Sigma n^2-2 \Sigma n-3 \Sigma 1\end{aligned}\)…