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1+2+3+.............................80

Răspuns :

suma lui Gauss:
s= n(n+1)/2
s= 80(80+1)/2
s= 80•81/2
s= 6480/2
s= 3240

S = 1 + 2 + .. + 80

S = 80*81 : 2

S = 3240