Question

VOTEZ CEL MAI BUN
Calculati
S = 2+4+6+....+500=
S = 1+4+7+.....+301=
S = 5+10+15+....+2000=
S = 51+52+....+100=
Astept un raspuns
multumesc

Answer 1

1)
S=2(1+2+3+..........+250)
aplicand formula 
S=2x(1+250)x250/2=62750
2)
cati termeni sunt in suma?
n=(an-a1+r)/r=(301-1+3)/3=101 termeni
S=(1+301)x101/2=15251
3)
S=5(1+2+........+400)=5x(1+400)x400/2=401000
4)
S=51+52+.....+100=(51+100)x50/2=3775