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4/1•5+4/5•9+4/9•13+...+4/2004•2008=?

4154594913420042008 class=

Răspuns :

Descompunem fractiile :
  4/1*5=1/1-1/5  vom avea:  1/1-1/5 + 1/5-1/9 + 1/9-1/13 + ... +1/2004-1/2008 = 1/1-1/2008=
⇒(2008-1)/2008=2007/2008
   acestea doi cate doi se reduc (=0)