DAU COROANA !!

5/7 + 7/3 + 9/4 + .... + 401/200 - (1/2 + 1/3 + 1/4 + ... + 1/200)


Răspuns :

5/2 + 7/3 + 9/4 + .... + 401/200 - (1/2 + 1/3 + 1/4 + ... + 1/200) =
=5/2-1/2+7/3-1/3+9/4-1/4+.....+401/200-1/200=
=4/2+6/3+8/4+....+400/200=
=2+2+2+....+2=2×199=398
nr termeni   200-2+1=198+1=199