Răspuns :
Răspuns:
5+10+15+20+….2020=5[404(404+1):2]=5·163620:2=409050
5+10+15+20+......2020
5•(1+2+3+4+......+404)
5•404•(404+1):2
2020•4045:2=8170900:2=4085450
5•(1+2+3+4+......+404)
5•404•(404+1):2
2020•4045:2=8170900:2=4085450