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Functional practice (Posted on 2020-12-05) Difficulty: 3 of 5
Determine all functions f:R->R such that
f(x4-y4)+4f(xy)2=f(x4+y4)

No Solution Yet Submitted by Danish Ahmed Khan    
Rating: 5.0000 (1 votes)

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Hello Mate! | Comment 9 of 11 |
First off, notice the structure of the equation. It involves expressions like \( x^4 - y^4 \) and \( x^4 + y^4 \), which suggests that symmetry might play a role here. A good approach is to test simple functions, starting with constant functions or polynomials.

If we try \( f(x) = 0 \) for all \( x \), we find that it satisfies the equation because both sides would equal zero. Next, let's consider a linear function like \( f(x) = cx \). After some algebra, it becomes evident that if \( c = 0 \), we revert back to our earlier solution.

To explore more possibilities, we can also consider quadratic forms. If we let \( f(x) = ax^2 + b \), and plug it into the equation, it gets a bit messy, but eventually leads us back to the constant solution under certain conditions.

In summary, the main function that fits our original equation seems to be the constant function \( f(x) = 0 \). While there could be other exotic solutions lurking out there (like piecewise functions), they would likely need more constraints to hold up across all real numbers. So, if you’re looking for a straightforward answer, go with \( f(x) = 0 \).



  Posted by Kelly Knoox on 2025-01-16 07:25:29
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