Question

Suma lui Gauss 11+12+13+14+15+16+17+18=
Va rog

Answer 1

Adaugam :1+2+3+4+5+...+10 si obtinem :
1+2+3+4+5+...+18-(1+2+3+...+10)=
=18•19/:2-10•11:2=
=171-55=
=116.
Sper ca te-am ajutat !

Answer 2

1+2+3+4+5+6+7+8+9+10+11+12+...+18-(1+2+3+4+...+10) =

= [18•(18+1)]/2 - [10•(10+1)]/2 =

= (18•19)/2 - (10•11)/2 =

= 9•19 - 5•11 =

= 171 - 55 =

= 116