Question

Tính tổng các đại số sau

a) -1-2-3-4-5-............-2009-2010

b) 1-3+5-7+...... ..+2005-2007+2009-2011

c) 1-2-3+4+5-6-7+...............+1997-1998-1999+2000+2001

Answer 1

a) -1 - 2 - 3 - 4 - 5 -.............- 2009 - 2010

SCSH: ( 2010 - 1 ) : 1 + 1 = 2010

tỔNG: ( 2010 + 1 ) . 2010 : 2 = 2021055

b) 1 - 3 + 5 - 7 +...............+ 2005 - 2007 + 2009 - 2011

SCSH: ( 2011 - 1 ) : 2 + 1 = 1006

tỔNG: ( 2011 + 1 ) . 1006 : 2 = 1012036

c) 1 - 2 - 3 + 4 + 5 - 6 - 7 +..........................+ 1997 - 1998 - 1999 + 2000 + 2001

SCSH: ( 2001 - 1 ) : 1 + 1 = 2001

tỔNG: ( 2001 + 1 ) . 2001 : 2 = 2003001

Hk tốt,

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