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Larisaoprea9
a fost răspuns

1+2-3+4+5-6+7+8-9+...+2008+2009-2010+2011

Răspuns :

CarMina03
1+2-3+4+5-6+7+8-9+.....+2008+2009-2010+2011
observam ca 1+2-3=0; 4+5-6=3; 7+8-9=6; ....;2008+2009-2010=2007
deci suma devine 0+3+6+...+2007+2011= 3(1+2+3+...+669)+2011= 3*(669*670):2+2011=3*669*335+2011=674356


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