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a fost răspuns

1/1*5+1/5*9+1/9×13+....+1/41*45​

Răspuns :

Matemovici

Suma telescopica

1/a*b = 1/a - 1/b

1/1*5 + 1/5*9 + ... + 1/41*45

1/1 -1/5 + 1/5 - 1/9 + ... 1/41 - 1/45 (se simplifca termenii -1/5+1/5 etc)

1/1-1/45 = 44/45