Question

suma lui Gauss 3+5+7+...+79

Answer 1

Poti rezolva folosing formula:
(primul+ultimul) * nr termeni / 2 si rezulta
82*39/2=1599

Sper ca te-am ajutat.

Answer 2

S = 3 + 5 + 7 + ...... + 79

→ stabilesc cati termeni are suma, cu ratia 2 ( 5 - 3 = 2;   7 - 5 =2;... )

( 79 - 3 ) : 2 + 1 = 76 : 2 + 1 = 38 + 1 = 39 termeni are suma

→ aplic formula sumei lui Gauss

S = 39 × ( 3 + 79 ) / 2

S = 39 × 82 / 2

S = 39 × 41

S = 1 599