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JEE Mains · Maths · STD 12 - 1. relation and function

माना \(f ( x )=\frac{ x -1}{ x +1}, x \in R -\{0,-1,1)\) है। यदि \(f ^{ n +1}( x )= f \left( f ^{ n }( x )\right)\) है, तो \(\forall n \in N\), है, तो \(f ^6(6)+ f ^7(7)\) बराबर है

  1. A \(\frac{7}{6}\)
  2. B \(-\frac{3}{2}\)
  3. C \(\frac{7}{12}\)
  4. D \(-\frac{11}{12}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(-\frac{3}{2}\)

Step-by-step Solution

Detailed explanation

\(f(x)=\frac{x-1}{x+1}\) \(\Rightarrow f^{2}(x)=f(f(x))=\frac{\frac{x-1}{x+1}-1}{\frac{x-1}{x+1}+1}=-\frac{1}{x}\) \(f^{3}(x)=f\left(f^{2}(x)\right)=f\left(-\frac{1}{x}\right)=\frac{x+1}{1-x}\) \(\Rightarrow f^{4}(x)=f\left(\frac{x+1}{1-x}\right)=-\frac{1}{x}\)…
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