a, 15/25 - 3/21 = 3/5 - 1/7 = 21/35 - 5/35 = 18/35

b, 24/36 - 6/12 = 2/3 - 1/2 = 4/6 - 3/6 = 1/6

a)15/25-3/21=3/5-1/7=16/35                b)24/36-6/12=2/3-1/2=1/6

\(\dfrac{5}{17}\times\dfrac{34}{25}=\dfrac{5\times17\times2}{17\times5\times5}=\dfrac{2}{5}\)

\(\dfrac{5}{17}\times\dfrac{34}{25}=\dfrac{5\times34}{17\times25}=\dfrac{170}{425}=\dfrac{2}{5}\)

= nhau nha

\(2/3*4/5=8/15\)

\(4/5*2/3=8/15\)

\(=>2/3*4/5=4/5*2/3\) nhé

1/4 có rút gọn rồi nha 

nhưng cậu có thể giải thích là tại sao lại là \(\dfrac{1}{4}\) ko?

\(\dfrac{8}{11};\dfrac{8}{9};\dfrac{8}{5}\)

8/11; 8/9; 8/5

a: 

13/17=1-4/17

8/12=1-4/12

mà 4/17<4/12

nên 13/17>8/12=12/18

b: 16/51<17/51=1/3=30/90<31/90

12/18<13/17

16/51>31/90

\(\dfrac{6}{7}+\dfrac{5}{8}=\dfrac{48}{56}+\dfrac{35}{56}=\dfrac{83}{56}\)

\(\dfrac{36}{12}-\dfrac{5}{3}=\dfrac{9}{3}-\dfrac{5}{3}=\dfrac{4}{3}\)

\(\dfrac{6}{7}+\dfrac{5}{8}=\dfrac{48}{56}+\dfrac{35}{56}=\dfrac{83}{56}\\\dfrac{36}{12}+\dfrac{5}{3}=\dfrac{36}{12}+\dfrac{20}{12} =\dfrac{56}{12}=\dfrac{14}{3}\)

a: 4/9+3/7=28/63+27/63=55/63

3/4+7/24=18/24+7/24=25/24

1/3+2/9+4/27=9/27+6/27+4/27=19/27

b: 5/6-3/8=20/24-9/24=11/24

7/15-11/30=14/30-11/30=3/30=1/10

2/3+1/6-7/12

=8/12+2/12-7/12

=3/12=1/4

c: 18/25*15/6=15/25*18/6=3*3/5=9/5

30/49:6/7=30/49*7/6=210/294=5/7

1/2*3/4:6/5=3/8*5/6=15/48=5/16

d: 8*3/5:12/5=24/5*5/12=2

4:9/5:10/3=4*5/9*3/10=2/3

thế là viết ra giấy à bn

Làm gì cũng được miễn là có lời giải và đáp án