Question

cat face /-1/+/-2/+/-3/+....+/-120/???

Answer 1

Modulul unui nr. este intotdeauna pozitiv.
1+2+3+...+120
Aplic formula sumei lui Gauss [n(n+1)]/2 => 1+2+...+120=120*121/2=60*121=7260

Answer 2

Daca /-1/ = modul de -1 , adica I-1I avem:

I-1I + I-2I +I-3I +...........+I-120I = 1+2+3+......+120 = (1+120)x120:2 = 60x121 = 7260