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Chiriacloredana67
a fost răspuns

10+20+30+.....+2020-9-18-27-.....1818 dau coroana

Răspuns :

Rayzen

10+20+30+...+2020

-9-18-27-...-1818 =

= 10•(1+2+3+...+202) -

- 9•(1+2+3+...+202)

= (10-9)•(1+2+3+...+202)

= 1•(1+2+3+...+202)

= 1+2+3+...+202

= [(202•(202+1)]/2

= (202•203)/2

= 101•203

= 100•203 + 203

= 20300 + 203

= 20503

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