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1. 5+10+15+.....+2005+2010+2015
2. 1+7+13+.....+2005+2011+2017
REPEDE VA ROG


Răspuns :

Răspuns:

5 +10 + 15+...+2005+2010+2015

2015+2010+2005+...+15 + 10 + 5

------------------‐--------------------------------‐----------+

2020+2020+2020+...2020+2020+2020

5*1=5

5*2=10

5*3=15

'

'

'

5*401=2005

5*402=2010

5*403=2015

2S=2020x401

2s=810020

s=810020:2

s=405010

Explicație pas cu pas:

P.S NUSH DACA E BN