7+9+11+...+2015
Folosim formulele lui Gauss:
(2015-7):2+1=2008:2+1=1005(nr.termeni)
(2015+7)X1005:2=2008X1005:2=1.009.020(su-
ma)
1.009.020-5-7-9-...-2011
1.009.020-(5+7+9+...+2011)=
5+7+9+...2011=
Folosim formulele lui Gauss:
(2011-7):2+1=
2004:2+1=
1002+1=
1003(nr. termeni)
(2011+7)X1003:2=
2018X1003:2=
2.024.054:2=
1.012.027(suma)
