S=(1-2-3+4)+(5-6-7+8)+...+(2001-2001-2003+2004)
S=0+0+....+0
S=0
S = 1-2-3+4+5-6-7+8+...+2001-2002-2003+2004
S = (1-2-3+4) + (5-6-7+8) + ...+ (2001-2002-2003+2004)
S = 0 + 0 + ...+ 0
S = 0
S = 1 - 2 - 3 + 4 + 5 - 6 - 7 + 8 + .... + 2002 - 2002 - 2003 + 2004
S = ( 1 - 2 - 3 + 4 ) + ( 5 - 6 - 7 + 8 ) + .... + ( 2001 - 2002 - 2003 + 2004 )
S = 0 + 0 + .... + 0
S = 0
Hok tốt !
Giải:
Ta có: A = 1 – 2 – 3 + 4 + 5 – 6 – 7 + 8 + … + 2001 – 2002 – 2003 + 2004
A = (1 – 2 – 3 + 4) +( 5 – 6 – 7 + 8) + … + (2001 – 2002 – 2003 + 2004)
A = 0 + 0 + … + 0 = 0.