C1:
(1/4+1/7)x1/3=11/28x1/3

                   =11/84

C2:

(1/4=1/7)x1/3=1/3x1/4+1/3x1/7
                   =1/12+1/21

                   =11/84

cho mk nhé, có fb kb vs mk đi nè <3 <3

\(\left(\dfrac{1}{4}+\dfrac{1}{7}\right)\times\dfrac{1}{3}\\ =\left(\dfrac{7}{28}+\dfrac{4}{28}\right)\times\dfrac{1}{3}\\ =\dfrac{11}{28}\times\dfrac{1}{3}\\ =\dfrac{11}{84}\)

C1:

\(\left(\dfrac{1}{4}+\dfrac{1}{7}\right)\times\dfrac{1}{3}\\ =\left(\dfrac{7}{28}+\dfrac{4}{28}\right)\times\dfrac{1}{3}\\ =\dfrac{11}{28}\times\dfrac{1}{3}\\ =\dfrac{11}{84}\)

C2:

\(\left(\dfrac{1}{4}+\dfrac{1}{7}\right)\times\dfrac{1}{3}\\ =\dfrac{1}{4}\times\dfrac{1}{3}+\dfrac{1}{7}\times\dfrac{1}{3}\\ =\dfrac{1}{12}+\dfrac{1}{21}\\ =\dfrac{7}{84}+\dfrac{4}{84}\\ =\dfrac{11}{84}\)

(1/4 + 1/7) x 1/3

= 11/28 x 1/3

= 11/84

(1/4 + 1/7) x 1/3

= 1/4 x 1/3 + 1/7 x 1/3

= 1/12 + 1/21

= 11/84

Giải đấy đủ giúp mình với 

a: =8/15x1/4=2/15

b: \(=\dfrac{5}{3}\cdot\dfrac{4}{5}\cdot\dfrac{6}{7}=\dfrac{24}{21}=\dfrac{8}{7}\)

c: \(=\dfrac{2}{5}\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{2}{5}\)

1 1/3 x 1 1/4 x 1 1/5 x 1 1/6 x 1 1/7 x 1 1/8 = 4/3 x 5/4 x 6/5 x 7/6 x 8/7 x 9/8 = 4x5x6x7x8x9/3x4x5x6x7x8 = 9/3 = 3

=3/2*4/3*5/4...*11/10

=5,5

\(1\frac{1}{2}\times1\frac{1}{3}\times1\frac{1}{4}\)

=\(\frac{3}{2}\times\frac{4}{3}\times\frac{5}{4}\)

=3-3\4-4x\(\frac{5}{2}\)

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

5 phan 2

\(1\frac{1}{2}.1\frac{1}{3}.1\frac{1}{4}=\frac{3}{2}.\frac{4}{3}.\frac{5}{4}=2.\frac{5}{4}=\frac{5}{2}\)

a) 563 x 23 + 23 x 28 - 23

= 23 x (563 + 28 - 1)

= 23 x 600

= 19200

b) \(\frac{7}{11}+\frac{3}{4}+\frac{4}{11}+\frac{1}{4}-1\frac{2}{5}=\left(\frac{7}{11}+\frac{4}{11}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)-\frac{7}{5}=2-\frac{7}{5}=\frac{3}{5}\)

c) \(\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)\times...\times\left(1-\frac{1}{10}\right)=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times....\times\frac{9}{10}\)

\(=\frac{1\times2\times3\times...\times9}{2\times3\times4\times...\times10}=\frac{1}{10}\)

d) \(\frac{2}{7}\times\frac{3}{9}+\frac{2}{7}\times\frac{2}{3}=\frac{2}{7}\times\left(\frac{3}{9}+\frac{2}{3}\right)=\frac{2}{7}\times1=\frac{2}{7}\)

a ) \(563\cdot23+23\cdot28-23\)

\(=23\cdot\left(563+28-1\right)\)

\(=23\cdot600\)

\(=19200\)

b ) \(\frac{7}{11}+\frac{3}{4}+\frac{4}{11}+\frac{1}{4}-1\frac{2}{5}=\left(\frac{7}{11}+\frac{4}{11}\right)+\left(\frac{3}{4}+\frac{1}{4}\right)-\frac{7}{5}=2-\frac{7}{5}=\frac{3}{5}\)

c ) \(\left(1-\frac{1}{2}\right)\cdot\left(1-\frac{1}{3}\right)\cdot\left(1-\frac{1}{4}\right)\cdot...\cdot\left(1-\frac{1}{10}\right)=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot...\cdot\frac{9}{10}\)

\(=\frac{1\cdot2\cdot3\cdot...\cdot9}{2\cdot3\cdot4\cdot...\cdot10}=\frac{1}{10}\)

d ) \(\frac{2}{7}\cdot\frac{3}{9}+\frac{2}{7}\cdot\frac{2}{3}=\frac{2}{7}\cdot\left(\frac{3}{9}+\frac{2}{3}\right)=\frac{2}{7}\cdot1=\frac{2}{7}\)

\(...=\dfrac{3}{2}x\dfrac{4}{3}x\dfrac{5}{4}x\dfrac{6}{5}x\dfrac{7}{6}....x\dfrac{1000}{999}\)

\(=\dfrac{1}{2}x\dfrac{1000}{1}=500\)

=3/2x4/3x5/4x....x1000/999

=1/2x1000=500

mình chưa chắc là đúng đâu nhé