We are tasked with finding all functions f:Z→Z such that if x+y+z=0, then f(x)+f(y)+f(z)=xyz.
To solve this problem, we start by considering the functional equation:
f(x)+f(y)+f(z)=xyz
for any integers x,y,z satisfying x+y+z=0.
Step 1: Use Zero Argument
Set x=y=z=0, then f(0)+f(0)+f(0)=0. Therefore, we have:
3f(0)=0⇒f(0)=0.
Step 2: Explore Linear Functions
Assume a linear form for the function f, i.e., f(x)=ax3+bx2+cx+d.
Substitute z=−x−y into the equation:
f(x)+f(y)+f(−x−y)=xyz.
Step 3: Symmetry Considerations
Exploiting the symmetry x+y+z=0, analyze:
- Setting z=−x−y gives:
f(x)=3x3−x+tx, where t∈Z.
This form arises from identifying potential polynomial solutions and checking their consistency through known identities and special cases.
Step 4: Verification
To verify our candidate function:
- f(x)=3x3−x+tx satisfies:
f(x)+f(−x)+f(0)=xyz
when substituting into the equation.
Final Answer
Thus, all functions satisfying the given condition are of the form:
f(x)=3x3−x+tx for any t∈Z.
The complete set of functions is:
f(x)=3x3−x+tx for any t∈Z