Question

determenati suma
S=3+6+9...+2013
va rog dau 30 p

Answer 1

S = 3 + 6 + 9 + ...  + 2013 

S = 3 × ( 1 + 2 + 3 + ... + 671 )

S = 3 × 671 × 672 : 2 

S = 3 × 225456

S = 676368

Answer 2

S=3(1+2+3+.......+671)
A=1+2+......+671
A=671+670+....+1
adunând cele două sume
2×A=672+672+...+672 de 671 ori
A=672×671/2
A=336×671
A=225456
S=3×225456
S= 676368