a=1+2+3+...+2013 de aflat a

Răspuns :

a = 1 + 2 + 3 + ........ + 2013

a = 2013 × ( 1 + 2013 ) / 2 → am aplicat formula sumei lui Gauss

a = 2013 × 2014 / 2

a = 2013 × 1 007

a = 2 027 091

Suma lui gaus:

2013* (2013+1):2
2013*2014:2
4054182:2
2027091