Răspuns :
1+3+5...+99= (99x100:2) - 2x(1+2....+49)
= 99x50- 2x 49x50:2
= 99x50-98x25
=4950-2450
=2500
= 99x50- 2x 49x50:2
= 99x50-98x25
=4950-2450
=2500
I : 1
II : 99
||| : 100\2 = 50
IV : ( I+II) ·III \2
= 50 ·50 \2
=100 \2
50
II : 99
||| : 100\2 = 50
IV : ( I+II) ·III \2
= 50 ·50 \2
=100 \2
50