reserve a,b,n for Element of NAT;

theorem Th34:
  for a,b,n being Nat holds GenFib(a,b,n) + GenFib(a,b,n+1) = GenFib(a,b,n+2)
proof
  let a,b,n be Nat;
  GenFib(a,b,n) + GenFib(a,b,n+1) = GenFib(a,b,n+1+1) by Th32
    .= GenFib(a,b,n+2);
  hence thesis;
end;
