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calculati 1/1×2+1/2×3+1/3×4+...+1/2013×2014

Răspuns :

1/1×2+1/2×3+1/3×4+...+1/2013×2014 =

= 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 +...+ 1/2013 - 1/2014 =
(se reduc termenii)
= 1/1 - 1/2014 =

= (2014 - 1)/2014 =

= 2013/2014