Răspunsuri

2014-11-08T14:44:40+02:00
5*(1+2+....+20)=si faci 5 ori suma lui Gaus la paranteza ;)

2014-11-08T16:09:33+02:00
5+10+15+........+100=5·(1+2+..+20)=5·20·21:2=1050