1. Given that f(w,w,w)=0 for all w∈R, we need to show that there exist polynomials A(x,y,z), B(x,y,z), and C(x,y,z) such that A+B+C=0 and
f(x,y,z)=A(x,y,z)⋅(x−y)+B(x,y,z)⋅(y−z)+C(x,y,z)⋅(z−x).
2. Let C=−A−B. Then we can rewrite f as:
f=A⋅(x−y)+B⋅(y−z)+(−A−B)⋅(z−x).
Simplifying this, we get:
f=A⋅(x−y)+B⋅(y−z)−A⋅(z−x)−B⋅(z−x).
f=A⋅(x−y)−A⋅(z−x)+B⋅(y−z)−B⋅(z−x).
f=A⋅(x−y+x−z)+B⋅(y−z+x−z).
f=A⋅(2x−y−z)+B⋅(y+x−2z).
3. We need to show that there exists a polynomial B such that A=y−2x+zB⋅(y+x−2z)−f is a polynomial.
4. Consider f as a polynomial in y and perform the division of f by (y+x−2z). We get:
f=g⋅(y+x−2z)+h,
where h is a polynomial in x and z.
5. From the condition f(w,w,w)=0, we have:
0=f(w,w,w)=g(w,w,w)⋅(w+w−2w)+h(w,w).
This implies that h(w,w)=0 for every real w.
6. It is well-known that x−z divides h, so we let h=s⋅(x−z), where s is a polynomial in x and z.
7. Therefore, we have:
A=−g+y−2x+zB⋅(y+x−2z)−s⋅(x−z).
8. Let B=B1⋅(y−2x+z)+3s. Then we have:
A=−g+B1⋅(y+x−2z)+y−2x+z3s⋅(y+x−2z)−s⋅(x−z).
Simplifying, we get:
A=−g+B1⋅(y+x−2z)+s,
which is clearly a polynomial.
9. Since there are infinitely many polynomials B1 we can choose, there is no polynomial f such that A, B, and C can be uniquely determined.