Section test.
Context {A:Type}`{Aid:Integral_domain A}.

Lemma example4 : forall x y z u,
x+y+z+u==0 ->
x*y+x*z+x*u+y*z+y*u+z*u==0->
x*y*z+x*y*u+x*z*u+y*z*u==0->
x*y*z*u==0 -> x^4%Z==0.