reserve a,b,c,d,x,j,k,l,m,n for Nat,
  p,q,t,z,u,v for Integer,
  a1,b1,c1,d1 for Complex;

theorem
  b>0 & a>b implies
  ((a|^n-b|^n)*(a+b) = (a|^n+b|^n)*(a-b) iff n=1) by Lm57d;
