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Question: Answered & Verified by Expert
If 2f xy = f x y + f y x for all x,yR and f 1 =3, then the value of Σ r = 1 1 0 f r  is equal to
MathematicsFunctionsJEE Main
Options:
  • A 3 2 3 1 0 - 1
  • B 3 2 3 9 - 1
  • C 3 1 0 - 1 2
  • D 12310-1
Solution:
2900 Upvotes Verified Answer
The correct answer is: 3 2 3 1 0 - 1
From given functional equation,  2f xy = f x y + f y x ,x,yR

putting y=1 ,

2f x =f x + f 1 x

f x = 3 x

∴     Σ r = 1 1 0 f r = Σ r = 1 1 0 3 r = 3 3 1 0 - 1 3 - 1 = 3 2 3 1 0 - 1

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