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  • Utilizator Brainly
2014-10-04T11:00:33+03:00
5+10+15+...+40 /:5 => dam factor comun pe 5 si rezulta
1+2+3+.........+8


Acum folosesti formula n(n+1):2 .

S=1+2+3+..........+8
S=8(8+1):2
S=36
5+10+15+........+40=5*36=180


8 3 8
2014-10-04T12:41:56+03:00
5+10+15+..+40=5   (1+2+...+8)=5x8x9:2=180
4 4 4