Question

S =(-3)+(-2)+(-1)......+(25)+(26)+(27)=

Answer 1

S=(-3-2-1+0)+(1+2+3+...+27)=-6+27*28/2=-6+27*14=-6+378=372.

Answer 2

S =(-3)+(-2)+(-1)......+(25)+(26)+(27)=
se imparte in doua
S=S1+S2
unde S1=(-3)+(-2)+(-1)+0= - 6
S2=1+2+3+4+....+25+26+27 care este suma Gauss, termeni consecutivi si incepe din 1
are formula de calcul S=[n(n+1)]:2

S2=1+2+3+4+....+25+26+27=(27*28):2=378
S= - 6 +378

S = 372

S =(-3)+(-2)+(-1)......+(25)+(26)+(27)=372