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Efectuand calculul : ( 3/2+4/3+5/4+....+1909/1908) - ( 1/2+1/3+1/4+...+1/1908 ) veti obtine anul in care a aparut automobilul Tin Lizzy

Răspuns :

(3/2+4/3+....1909/1908)-(1/2+1/3+....+1/1908)=
(1/2+2/2+1/3+3/3+...+1/1908+1908/1908)-(1/2+1/3+...+1/1908)
1/2+1/3+....+1/1908+ 1+1+....+1-(1/2+1/3+...+1/1908)=1*1907=1907
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                         =0
 ( 3/2+4/3+5/4+....+1909/1908) - ( 1/2+1/3+1/4+...+1/1908 )
2/2+3/3+4/4+...+1098/1098=1+1+...+1 ( de 1907 ori) =1907