Răspunsuri

2014-09-16T22:49:42+03:00
Folosesti formula 1/n-1/n+1=1/n*(n+1)
si obtii:
1/10*11+1/11*12+1/12*13+1/13*14+1/14*15=1/10-1/11+1/11-1/12+1/12-1/13+1/13-1/14+1/14-1/15=1/10-1/15=3/30-2/30=1/30