Chứng minh rằng: (1 + 1/3 + 1/5 + ... + 1/1999) - (1/2 + 1/4 + ... + 1/2000) = 1/1001 + 1/1002 + ...+ 1/2000, Chứng minh rằng: (1 + 1/3 + 1/5 + ... + 1/1999) - (1/2 + 1/4 + ... + 1/2000) = 1/1001 + 1/1002 + ... + 1/2000