Question

Calculati sumele

1+2+3+........+121=

Answer 1

s=1+2+3+...+121
S= $\frac{121*122}{2}$
S=$\frac{14762}{2}$
S=7381

Answer 2

    S=1+2+3+...+121⇔formula lui Gauss[n*(n+1)]:2
  ⇔S=[121*(121+1)]:2 simplificam 122(obtinut din 121+1) cu 2 prin 2
  ⇔S=121*61⇔S=7381