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17+18+19+..........+59=

Răspuns :

59×60:2=1779 spee ca team ajutat
progresie aritmetica cu ratia 1
stim ca an=a1+(n-1)R=>59=17+n-1=>n=43
stim ca sn=(a1+an)n/2
sn=(17+59)43/2=76*43/2=1634
sn=1634