Question

Dau o gramada de puncte+coroana (am nevoie de problema urgent pana desearaa) va rog muuult

Answer 1

1/3+1/6+1/10+...+2/2017*2018=

2/2*3+2/3*4+2/4*5.....+2/2017*2018=

2(1/2*3+1/3*4+.1/4*5+...+1/2017*2018)=

2( 1/2-1/3+1/3-1/4+1/4-1/5+...+1/2017-1/2018)=

2(1/2-1/2018)=

2*(1/2)*(1-1/1014)=

1-1/1014=1014/1014=1/1014

=1013/1014

adica un fel de treișpe-paișpe, dar cu altă pălărie...::)))