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x(1+1/2+1/3+1/4+.....1/2015)=2015-1/2-2/3-3/4-....-2014/2015

Răspuns :

2015=1+1+1........+1 de 2015 ori si atunci
2015-1/2-2/3-.......2014/2015=1+(1-1/2)+(1-2/3)+(1-3/4)+..........+(1-2014/2015)=
1+1/2+1/3+..........+1/2015
deci
x(1+1/2+1/3+......+1/2015)=(1+1/2+1/3+..........+1/2015)
x=1