Question

efectuati:
7+9+11+....+2013-5-7-9....-2011

Answer 1

Observam :7-5=2, 9-7=2, 11-9=2........2013-2011=2

2x3+1=7,2x4+1=9...2x1006+1=2013

1006-3+1=1004

2x1004=2008

SAU

7+9+...+2013-( 5+7+....+2011)

Metoda contorului

2x3+1=7, 2x4+1=9,..., 2x1006+1=2013

1006-3 +1=1004

S=       7+ 9+  ........    + 2013

S=2013+2011+..........+     7

________________________

2020+ 2020+.......2020 de 1004 ori

2020x1004=2028080

2028080: 2=1014040

2x2+1=5, 2x3+1=7.......2x1005+1=20111005-2+1= 1004

S=       5+ 7+...........+2011

S= 2011+2009+......+5

_____________________

2016 +2016.....+2016 DE 1004 ORI

1004X2016= 2024064

2024064:2= 1012032

1014040-1012032=2008