(1/2+1/3+1/4+...+1/20)+(19/20+18/19+...+3/4+2/3+1/2)

Răspuns :

(1/2+1/2)+(1/3+2/3)+(1/4+3/4)+(1/5+4/5)+(1/6+5/6)+(1/7+6/7)+(1/8+7/8)+(1/9+8/9)+(1/10+9/10)+(1/11+10/11)+(1/12+11/12)......…...........................(1/19+18/19)+(1/20+19/20)=1+1+1+1+1....+1=19