5+10+15+20+...+2020 calculeaza prin suma lui gaus

Răspuns :

5+10+15+...+2020=
=5(1+2+3+...+404)=
=5×404×405:2=
=5×81810=
=409050

5+10+15+..+2020 =
= 5×(1+2+3+..+404)
= 5×404×405÷2
= 5×81810
= 409050