Question

a) (1/3•3+1/3•4+...+1/41•42)-3/21
b) (1/6•7+1/7•8+...+1/35•36)-(1/1•2+1/2•3+...+1/71•72)
c) (2/1•3+2/3•5+...+2/2015•2017)-( -1/2017)

Answer 1

fiecare 1 de la numarator se scrie ca diferenta intre factorii numitorului apoi descompunem in doua fractii. De exemplu 1/5*6=6-5/5*6=6/5*6 - 5/5*6=1/5-1/6. procedand asa cu toate fractiile si anuland termenii de forma +a-a, in paranteza ramane 1-1/42 adica 41/42.