Question

Calculatimi va rog: 5+6+.....+121 si 2+3+4+.....+61

Answer 1

Se foloseste suma lui Gauss

1+2+3+4+5+6+...121=121x(121+1):2=121x122:2=121x61=7381
1+2+3+4=10
5+6+...121=7381-10=7371

1+2+3+4+.....+61=61x(61+1):2=61x62:2=61x31=1891
2+3+4+.....+61=1891-1=1890