= (1+1/3+1/5+…+1/99)-(1/2+1/4+….+1/100)
= (1+1/2+1/3+…+1/100)-2(1/2+1/4+1/6+…+1/100)
= (1+1/2+1/3+…+1/100)-(1+1/2+1/3+…+1/50)
=1/51+1/52+…+1/100=VP (đpcm)
= (1+1/3+1/5+…+1/99)-(1/2+1/4+….+1/100)
= (1+1/2+1/3+…+1/100)-2(1/2+1/4+1/6+…+1/100)
= (1+1/2+1/3+…+1/100)-(1+1/2+1/3+…+1/50)
=1/51+1/52+…+1/100=VP (đpcm)