N=1-5-9+13+17-21-25+...+2001-2005-2009+2013

N=(1-5-9+13)+(17-21-25+29)+,,,,,+(2001-2005-2009+2013)

N=0+0+.....+0

N=0

Vay N=0

\(A=1-5-9+13+17-21-25+29+.......+2001-2005-2009+2013+2017\)\(A=\left(1-5-9+13\right)+.........+\left(2001-2005-2009+2013\right)+2017\)

\(A=0+0+...............+2017\)

\(A=2017\)

giúp mình nha mai mình cần gấp rồi

Ta có:

N= (1-5-9+13) + (17-21-25) +...+ ( 2001-2005-2009+2013)

N= 0 + 0 +...+ 0

N= 0

Vậy N=0.

Số hạng tử là:

( 2013 - 1 ) : 4 + 1 = 504 ( hạng tử )

N = ( 1 - 5 - 9 + 13 ) + ( 17 - 21 - 25 + 29 ) + ... + ( 2001 - 2005 - 2009 +2013 )

N = 0

N=1-5-9+13+17-21-25+......+2001-2005-2009+2013=0

k nha

Bài 2 : 

Ta có : 

\(A=1+3+3^2+...+3^{2012}\)

\(3A=3+3^2+3^3+...+3^{2013}\)

\(3A-A=\left(3+3^2+3^3+...+3^{2013}\right)-\left(1+3+3^2+...+3^{2012}\right)\)

\(2A=3^{2013}-1\)

\(A=\frac{3^{2013}-1}{2}\)

\(\Rightarrow\)\(A-B=\frac{3^{2013}-1}{2}-\frac{3^{2013}}{2}=\frac{3^{2013}-1-3^{2013}}{2}=\frac{-1}{2}\)

Vậy \(A-B=\frac{-1}{2}\)

Chúc bạn học tốt ~ 

thank you very mark