Question

Tính tổng:

S = 1 - 3 + 5 - 7 + ... + 2001 - 2003 + 2005

Answer 1

\(S=1-3+5-7+...+2001-2003+2005\)

\(=\left(1-3\right)+\left(5-7\right)+...+\left(2001-2003\right)+2005\)(Có 1002 cặp)

\(=\left(-2\right).1002+2005\)

\(=-2004+2005\)

\(=1\)

Answer 2

S = 1 - 3 + 5 - 7 + ... + 2001 - 2003 + 2005

= ( 1 - 3 ) + ( 5 - 7 ) + ... + ( 2001 - 2003 ) + 2005

= ( -2 ) + ( -2 ) + ... + ( -2 ) + 2005 ( có 1002 cặp -2 )

= ( -2 ) . 1002 + 2005

= -2004 + 2005

= 1