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Question


If f(x)+2f(1x)=x2+1  xϵR then f(x) is


Options:
A .   13(x2+4x3)
B .   23(x2+4x3)
C .   13(x24x+3)
D .   23(x24x+3)
Answer: Option C
:
C

f(x)+2f(1x)=x2+1   .........(i)
Replacing x by 1 – x
f(1x)+2f(x)=(1x2)+1  .......(ii)
multiplying (ii) by 2 and subtracting it from (1), we get
3f(x)=x22(1x)21
3f(x)=2(1x)2+1x2=(1x)(22x+1+x)=(1x)(3x)=x24x+3
f(x)=13(x24x+3)

 



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