Răspuns :
Completam suma ca sa avem o forma de suma Gauss ...
4+5+6+...+55 = (1+2+3)+4+5+6+...+55 - (1+2+3) =
__________________ ______
↓ ↓
55*56/2 - 6 = 1540-6 = 1534
4+5+6+...+55 = (1+2+3)+4+5+6+...+55 - (1+2+3) =
__________________ ______
↓ ↓
55*56/2 - 6 = 1540-6 = 1534