S = ( 1 + 2 - 3 - 4 ) + ( 5 + 6 - 7 - 8 ) + ... + ( 2001 + 2001 - 2003 - 2004 ) + ( 2005 + 2006 )

S = ( - 4 ) + ( - 4 ) + .... + ( - 4 ) + ( 2005 + 2006 )

Dãy S có : 2004 - 1 : 1 + 1 = 2004 số hạng

Dãy số S : 2004 : 4  = 501 số ( - 4 )

Dãy đó S = -4 x 501 = -2004 

S = -2004 + ( 2005 + 2006 ) 

S = -2004 + 4011

S = 2007

= ( 1 + 3 + 5 + ... + 2011 ) - ( 2 + 6 + 8 + ... + 2010 )

= [ 1006 x ( 2011 + 1 ) : 2 ] - [ 1005 x ( 2010 + 2 ) : 2 ]

= ( 1006 x 2012 : 2 ) - ( 1005 x 2012 : 2 )

= ( 2024072 : 2 ) - ( 2022060 : 2 )

= 1012036 - 1011030

= 1006

m giong ban kia !ban nao tk mk di !

1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + 9 + ... + 2006 - 2007 - 2008 + 2009 - 2010 - 2011 = 1006

\(248\times2006-2006-2006\times148=2006\times\left(248-1-148\right)=2006\times99=198594\)

Đây nha bn,nhớ tick cho mik nha 

248×2006−2006−2006×148=2006×(248−1−148)=2006×99=198594

2017*4+2017*62+2017*35-2017

=2017*(4+62+35-1)

=2017*100

=201700

2006*42+2006*39+2006*21-2006*2

=2006*(42+39+21-2)

=2006*100

=200600

 k mik đi

A , 201700

B, 200600

a) 2017*4+2017*62+2017*35-2017

=2017*(4+62+35)-2017*1

=2017*(101-1)

=2017*100

=201700

b)2006*42+2006*39+2006*21-2006*2

=2006*(42+39+21-2)

=2006*100

=200600

`3/4 +1/2 +1/4 +3/2`

`= (3/4+1/4)+(1/2+3/2)`

`= 4/4 + 4/2`

`=1+2`

`=3`

3/4+1/2+1/4+3/2

=(3/4+1/4)+(1/2+3/2)

=1+2

=3

\(\dfrac{2}{3}:\dfrac{4}{3}:\dfrac{5}{4}:\dfrac{1}{5}\)

=\(\dfrac{2}{3}\cdot\dfrac{3}{4}:\dfrac{5}{4}\cdot\dfrac{5}{1}\)

=\(\dfrac{1}{2}\cdot\dfrac{25}{4}\)

=\(\dfrac{25}{8}\)

\(\dfrac{1}{4}+\dfrac{2}{5}+\dfrac{3}{4}+\dfrac{3}{5}\)
\(=\left(\dfrac{1}{4}+\dfrac{3}{4}\right)+\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)
\(=1+1\)
\(=2\)

`1/4+2/5+3/4+3/5`

`=(1/4+3/4)+(2/5+3/5)`

`=4/4+5/5`

`=1+1`

`=2`

= ( 1/4 + 3/4 ) + ( 2/5 + 3/5 ) 

= 1 + 1

= 2

Có số số hạng là:

( 300- 1) : 1+ 1 = 300

Tổng dãy số trên là:

( 300+ 1) x 300 : 2 = 45150

               Đáp số: 45150

\(...=\left(300-1+1\right)\left(1+300\right):2=300.301:2=150.301=45150\)

=\(\frac{2}{5}+1\)

=\(\frac{7}{5}\)

\(\frac{2}{5}+\frac{3}{4}+\frac{1}{4}\)

\(=\frac{2}{5}+\left(\frac{3}{4}+\frac{1}{4}\right)\)

\(=\frac{2}{5}+1\)

\(=\frac{2}{5}+\frac{5}{5}\)

\(=\frac{7}{5}\)

Trả lời :

\(\frac{2}{5}+\frac{3}{4}+\frac{1}{4}\)

\(=\frac{2}{5}+1\)

\(=\frac{7}{5}\)