reserve a,b,n for Element of NAT;

theorem Th35:
  for a,b,n being Nat holds GenFib(a,b,n+1) + GenFib(a,b,n+2) =
  GenFib(a,b,n + 3)
proof
  let a,b,n be Nat;
  GenFib(a,b,n+1) + GenFib(a,b,n+2)= GenFib(a,b,((n+1)+1)+1) by Th32
    .= GenFib(a,b,n + 3);
  hence thesis;
end;
