\(\frac{2001x2003+2003x2005}{2003x4006}=\frac{2003x\left(2001+2005\right)}{2003x4006}\)

\(=\frac{2003x4006}{2003x4006}=1\)

\(\frac{2001x2003+2003x2005}{2003x4006}\)

=\(\frac{2003x.\left(2001+2005\right)}{2003x4006}\)

=\(\frac{2003x.4006}{2003x.4006}\)

=\(\frac{1.1}{1.1}\)

=1

`4/7xx3/7+4/5xx6/7-4/5xx7/14`

`=4/7xx3/7+4/5xx(6/7-7/14)`

`=4/7xx3/7+4/5xx5/14`

`=12/49+2/7`

`=26/49`

=4/7x3/7+4/5x(6/7-7/14)

=4/7x3/7+4/5x5/14

=12/49+2/7

=26/49

thank you bn

Lời giải:
$2\times A=\frac{2}{1\times 3}+\frac{2}{3\times 5}+\frac{2}{5\times 7}+...+\frac{2}{19\times 21}$
$2\times A=\frac{3-1}{1\times 3}+\frac{5-3}{3\times 5}+\frac{7-5}{5\times 7}+...+\frac{21-19}{19\times 21}$

$=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+....+\frac{1}{19}-\frac{1}{21}$

$=1-\frac{1}{21}=\frac{20}{21}$

$\Rightarrow A=\frac{20}{21}: 2= \frac{10}{21}$

= 5 x 7 + 5 x 4 + 5 x 8 + 5 x 1 

= 5 x ( 7 + 4 + 8 + 1 )

= 5 x 20 

= 100

5x(7+4+8+1)

=5x20

=100

5 x ( 7 + 8 + 5)

= 5 x 20

= 100

Ta lay 72 * 135 duoc 9720

Roi ta lay 9 * 28 *15 duoc 3780

Ta cong 9720 va 3780 duoc 13500

Ta lay 13500 / 25 duoc 540

Ta lay 3500 / 25 duoc 140

Cuoi cung ta lay 540 - 140 bang 400

nhu vay ket qua la 400

ban doc xong nho ket ban voi minh nhe

ta có:

( 72*135 + 9*15*28 ) : 25 - 3500 : 25 

= ( 72*135 + 135*28 - 3500 ) : 25  \ có 9*15=135; dùng tính chất phân phối phép nhân với phép cộng \

= [ 135*( 72 + 28 ) - 3500 ] : 25

= ( 13500 -3500 ) : 25

= 10000 : 25 = 400

\(=25,17\times\left(16,9-16,8\right)\\ =25,17\times1=25,17\)

25,17 x 16,9 - 25,17 x 16,8 

= 25,17 x ( 16,9 - 16,8 )

= 25,17 x 0,1

= 2,517

25,17 x 16,9 - 25,17 x 16,8

=25.17 x(16.9 - 16.8)

=25.17 x 0.1

=2.517

201,5*6,8+201,5*3,2

= 201,5 x ( 6,8 + 3,2 )

= 201,5 x 10

= 2015

201,5 x 6,8 + 201,5 x 3,2

= 201,5x ( 6,8 + 3,2 )

= 201,5 x 10

= 2015

k mk nha

Mk cảm ơn bạn nhiều

Thank you so much

= 201,5 x ( 6,8 + 3,2 )
= 201,5 x 10
= 2015

`29 xx 20,22 + 15 xx 20,22 + 20,22 xx 44 + 24 xx 10,11`

`= 20,22 xx (29 + 15 + 44 + 12)`

`= 20,22 xx 100`

`= 2022`

C1 : 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 24 x 10,11

= 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 12 x (2 x 10,11)

= 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 12 x 20,22

= 20,22 x 100

= 2022

C2: 29 x 20,22 + 15 x 20,22 + 20,22 x 44 + 24 x 10,11

= 20,22 x ( 29 + 15 + 44 + 12 )

= 20,22 x 100

= 2022

a 100*7+7+7+9=3000

a) (36 + 54) x 7 + 7 x 9 + 7=

= 90 x 7 + 7x 9 + 7 x1 = 

= 7 x ( 90 + 9 +1) =

= 7 x 100 = 700

b) 5/7 x 3 + 5/7 x 6 + 5/7 =

= 5/7 x (3 + 6 + 1) = 

= 5/7 x 10 = 50/7

( 36 + 54 ) x 7 + 7 x 9 + 7
=100 x 7 +7 x 9 +7
=7 x (100 x 9 x 1 )
=7 x 110
=770
\(\frac{5}{7}\times3+\frac{5}{7}\times6+\frac{5}{7}\)
\(=\frac{5}{7}\times\left(3+6+1\right)\)
\(=\frac{5}{7}\times10\)
\(=\frac{50}{7}\)