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Questions  

 A function f:RR satisfies the equation f(x)f(y)f(xy)=x+yx,yR and f(1)>0, then 

a
f(x)f−1(x)=x2−4
b
f(x)f−1(x)=x2−6
c
f(x)f−1(x)=x2−1
d
None of these

detailed solution

Correct option is C

Sol. (c) Taking x=y=1 , we get f(1)f(1)−f(1)=2⇒ f2(1)−f(1)−2=0⇒ (f(1)−2)(f(1)+1)=0⇒ f(1)=2        [ As f(1)>0] Taking y=1, we get  f(x)⋅f(1)−f(x)=x+1⇒f(x)=x+1⇒f−1(x)=x−1∴f(x)⋅f−1(x)=x2−1

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