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a fost răspuns

S= 2 plus 4 plus 6 plus 8 ................ plus 120

Răspuns :

S=2(1+2+3+4+...+60)
1+2+3+4+...+60=> aplicam formula [n(n+1)]:2 => [60(60+1)]:2 = (60x61):2 = 3660:2=1830
=> 2x1830=3660
S=3660