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efectuati:1+2+3+.......+57=

Răspuns :

1+2+3+...+57=57*58/2 = 1653
1+2+3+.....+57=[tex] \frac{n(n+1)}{2} [/tex]=[tex] \frac{57(57+1)}{2} [/tex]=[tex] \frac{3.306}{2} [/tex]=1.653