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

અહી \(f: R-\left\{\frac{\alpha}{6}\right\} \rightarrow R\) એ \(f(x)=\frac{5 x+3}{6 x-\alpha} \) દ્વારા આપવામાં આવ્યું છે તો  \(\alpha\) ની કઈ કિમત માટે દરેક \(x \in R-\left\{\frac{\alpha}{6}\right\}\) માટે  \((fof)(x)=x\) થાય.

  1. A \(4\)
  2. B \(5\)
  3. C \(6\)
  4. D \(8\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(5\)

Step-by-step Solution

Detailed explanation

\(f(x)=\frac{5 x+3}{6 x-\alpha}=y\,....(i)\) \(5 x+3=6 x y-\alpha y\) \(x(6 y-5)=\alpha y+3\) \(x=\frac{\alpha y+3}{6 y-5}\) \(f^{-1}(x)=\frac{\alpha x+3}{6 x-5}\,....(ii)\) fo \(f(x)=x\) \(f(x)=f^{-1}(x)\) From eq \(^{n}\) \((i)\, \& \,(ii)\) Clearly \(\alpha=5\)
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