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Given:-
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=> f(x) + 2f(1/x) =3x-----(1)
Now , we can also say ,
=> f(y) + 2f(1/y) =3y-----(2)
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Let y = 1/x
=> f(1/x) + 2f(x) = 3/x ----(3)
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Now ... lets do equation(3)×2
=> 2f(1/x) + 4f(x) = 6/x ---(4)
Now, equation (4) -(1)
=> 4f(x) - f(x) = (6/x) -3x
=> 3×f(x) = 3{(2/x)- x}
=> f(x) = (2/x) - x
=> f(x) =( 2 - x² )/x
to find the elements present in it,
we have ro make function f(x) =0.
so
=> f(x) = (2-x²)/x =0
=> f(x) = 2 - x² = 0 (since , x≠0)
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Note :-
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here , f(x) = 2-x² = f(-x)
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=> 2 - x² = 0
=> (x+ √2)(√2 -x)=0
So...
=> x = ±√2
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Hence, it contains exactly two elements.
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Hope (3) is your required answer
Proud to help you.
Answer:
x = +√2
Step-by-step explanation: