Question

1+2-3-4+5+6-7-8+9+10...+2005+2006-2007-2008+2009

Answer 1

\(1+2-3-4+5+6-7-8+...-2007-2008+2009\)

\(=\left(1+2-3-4\right)+\left(5+6-7-8\right)+...+\left(2005+2006-2007-2008\right)+2009\)

\(=\left(-4\right)+\left(-4\right)+\left(-4\right)+...+\left(-4\right)+2009\)

\(=\left(-4\right)\cdot502+2009\)

\(=\left(-2008\right)+2009\)

\(=1\)

Answer 2

bằng 1

Answer 3

1 + 2 - 3 - 4 + 5 + 6 - ... + 2006 - 2007 - 2008 + 2009

= 1 + ( 2 - 3 -  4 + 5 ) + ( 6 - 7 - 8 + 9 ) + ... + ( 2006 - 2007 - 2008 + 2009 )

= 1 + 0 + 0 + ... + 0

= 1