\(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot\dfrac{6}{5}\cdot\dfrac{5}{6}=\dfrac{1}{2}\cdot\dfrac{2}{3}=\dfrac{1}{3}\)

\(\dfrac{1}{2}\times\dfrac{2}{3}:\dfrac{5}{6}\times\dfrac{5}{6}\)

\(=\dfrac{1}{2}\times\left(\dfrac{2}{3}:\dfrac{5}{6}\times\dfrac{5}{6}\right)\)

\(=\dfrac{1}{2}\times\dfrac{2}{3}\)

\(=\dfrac{1}{3}\)

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

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

= 1 + 1 + 1 + 1

= 4

1+2+3+4+5+6+7+8+9 = ( 1+9) + ( 2+8) + (3+7) + (4+6) +5

= 10 + 10 + 10 + 10 + 5

= 45

(1+9)+(2+8)+(3+7)+(4+6)+5
=10 + 10 + 10 + 10
=40

2/3*(5/12+7/12) +1/3 = 2/3*12/12+1/3

= 2/3+1/3= 1

có khác gì câu ở trên của Linh Nguyễn Channel đâu trời

a.\(\dfrac{2}{3}\times\dfrac{4}{9}+\dfrac{2}{3}\times\dfrac{5}{9}=\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{2}{3}\times1=\dfrac{2}{3}\)

b.\(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\dfrac{3}{4}\times\left(\dfrac{7}{5}-\dfrac{1}{2}\right)=\dfrac{3}{4}\times\dfrac{9}{10}=\dfrac{27}{40}\)

c.\(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\dfrac{35}{24}\times\dfrac{2}{3}=\dfrac{35}{36}\)

a) 2/3 x 4/9 + 2/3 x 5/9 

=2/3 x ( 4/9 + 5/9)

= 2/3 x 1

=  2/3

b, 7/5 x 3/4 - 1/2 x 3/4

= ( 7/5 - 1/2 ) x 3/4

=     9/10         x 3/4

=         21/40

c, ( 5/6 + 5/8 ) x 2/3       

 =      35/24 x 2/3

=       35/36

a) \(\dfrac{2}{3}\times\dfrac{4}{9}+\dfrac{2}{3}\times\dfrac{5}{9}=\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{2}{3}\times1=\dfrac{2}{3}\)

b) \(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\left(\dfrac{7}{5}-\dfrac{1}{2}\right)\times\dfrac{3}{4}=\dfrac{9}{10}\times\dfrac{3}{4}=\dfrac{27}{40}\)

c) \(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\left(\dfrac{20}{24}+\dfrac{15}{24}\right)\times\dfrac{2}{3}=\dfrac{35}{24}\times\dfrac{2}{3}=\dfrac{35}{36}\)

=3/5 * ( 17/2 + 1/2 )

=3/5 * 9

=27/5

`2/3 xx 2/8 +2/3 : 8 +2/3 xx 5/8`

`=2/3 xx 2/8 +2/3 xx 1/8 +2/3 xx 5/8`

`=2/3 xx (2/8+1/8+5/8)`

`=2/3 xx 8/8`

`=2/3 xx 1`

`=2/3`

help me

mik ko biet

A=\(\frac{2}{1}\cdot3+\frac{2}{3}\cdot5+\frac{2}{5}\cdot7+\frac{2}{7}\cdot9\)

A=\(\frac{3}{1}\cdot2+\frac{5}{3}\cdot2+\frac{7}{5}\cdot2+\frac{9}{7}\cdot2\)

A=\(2\cdot\left(3+\frac{5}{3}+\frac{7}{5}+\frac{9}{7}\right)\)

A=\(2\cdot\frac{772}{105}\)

A=\(\frac{1544}{105}\)

A=\(14\frac{74}{105}\)

= 17/2 x 3/5 + 3/5 x 1/2 + 3/5 x 1 

= 3/5 x ( 17/2 + 1/2 + 1 ) 

= 3/5 x 10

= 30/5 

= 1/6

\(\frac{17}{2}\cdot\frac{3}{5}+\frac{3}{5}\cdot\frac{1}{2}+\frac{3}{5}\)

\(=\left(\frac{17}{2}+\frac{1}{2}+1\right)\cdot\frac{3}{5}\)

\(=\left(\frac{17}{2}+\frac{1}{2}+\frac{2}{2}\right)\cdot\frac{3}{5}\)

\(=10\cdot\frac{3}{5}=6\)

\(\frac{17}{2}\)x    \(\frac{3}{5}\)+    \(\frac{3}{5}\)x    \(\frac{1}{2}\)+    \(\frac{3}{5}\)=    \(\frac{17}{5}\)+    \(\frac{3}{10}\)+     \(\frac{3}{5}\)

                                                                         =     \(\frac{37}{10}\)+    \(\frac{3}{5}\)

                                                                         =     \(\frac{43}{10}\)