theorem
  n>0 implies t divides (t+z)|^n + (t|^n - z|^n)
  proof
    assume n>0; then
A1: t divides -t|^n by INT_2:10,Th6;
    t divides (t+z)|^n - z|^n + t|^n +(-t|^n) by Th10;
    hence thesis by A1,INT_2:1;
  end;
