Răspuns :
1+3+5+…+13 = x^2
1+3+5+…+13 = suma lui Gauss
intai aflam numarul de termeni
(13-1):2+1
12:2+1
6+1
=7 termeni
1+3+5+…+13= (1+13) x 7 :2
=14 x 7 :2
=7 x 7
7x7=x^2
7^2=x^2
=> x=7
1+3+5+…+13 = suma lui Gauss
intai aflam numarul de termeni
(13-1):2+1
12:2+1
6+1
=7 termeni
1+3+5+…+13= (1+13) x 7 :2
=14 x 7 :2
=7 x 7
7x7=x^2
7^2=x^2
=> x=7
Răspuns:
1+3+5+...+13=x²
(13-1):2 +1=7 → nr de elemente
S=[(1+13)·7]/2
S=(14·7)/2
S=98:2=>S=49
49=x²=>x=√49=>x=7