1/32<1/2x3
1/42<1/3x4
.......
1/1002<1/99x100
từ đây => 1/32+1/42+....+1/1002<1/2x3+1/3x4+1/4x5+........1/99x100
suy ra..........< 1/2-1/3+1/3-1/4+1/4-1/5................+1/99-1/100
hay............< 1/2 -100
hay........<1/2 vậy 1/32+1/42+.....+1/1002<1/2