4/1

4

4

4/7

12/21=12:3/21:3=4/7

4/7

1/2

1/2

1/2

mà anh hỏi sao là TV

\(\dfrac{1}{9}-\dfrac{8}{1}=\dfrac{1}{9}-\dfrac{72}{9}=\dfrac{-71}{9}\)

1/9- 8

= 1/9- 8/1

= 1/8- 72/9

= -71/9

\(\dfrac{5}{45}=\dfrac{5:5}{45:5}=\dfrac{1}{9}\);

\(\dfrac{40}{5}=\dfrac{40:5}{5:5}=\dfrac{8}{1}=8\)

\(\dfrac{1}{9}-8=\dfrac{1}{9}-\dfrac{72}{9}=-\dfrac{71}{9}\)

2/12=1/6

8/16=4/8=1/2

27/9=3

chúc bn học tốt

2/12=2:2/12:2=1/6

8/16=8:8/16:8=1/2

27/9=27:9/ 9:9 =3/1

\(\frac{2}{12}\)\(=\)\(\frac{1}{6}\)

\(\frac{8}{16}\)\(=\)\(\frac{1}{2}\)

\(\frac{27}{9}\)\(=\)1

a: =8/5-2/3=24/15-10/15=14/15

12/20-6/18=3/5-1/3=9/15-5/15=4/15

b: 18/21-12/27=6/7-7/9=54/63-49/63=5/63

8/12-20/50=2/3-2/5=10/15-6/15=4/15

\(a,\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{8}{5}-\dfrac{2}{3}=\dfrac{14}{15}\\ \dfrac{12}{20}-\dfrac{6}{18}=\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{4}{15}\\ b,\dfrac{18}{21}-\dfrac{12}{27}=\dfrac{6}{7}-\dfrac{4}{9}=\dfrac{26}{63}\\ \dfrac{8}{12}-\dfrac{20}{50}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)

a: \(=3\sqrt{3}-2\sqrt{3}+4\sqrt{3}-5\sqrt{3}=2\sqrt{3}\)

\(2\sqrt{27}-\sqrt{\dfrac{16}{3}}-\sqrt{48}-\sqrt{8\dfrac{1}{3}}\)

\(=6\sqrt{3}-4\sqrt{\dfrac{1}{3}}-4\sqrt{3}-5\sqrt{\dfrac{1}{3}}\)

\(=2\sqrt{3}-9\sqrt{\dfrac{1}{3}}\)

\(=2\sqrt{3}-3\sqrt{9\cdot\dfrac{1}{3}}\)

\(=2\sqrt{3}-3\sqrt{3}\)

\(=-\sqrt{3}\)

________________________

\(\left(\sqrt{125}-\sqrt{12}-2\sqrt{5}\right)\left(3\sqrt{5}-\sqrt{3}+\sqrt{27}\right)\)

\(=\left(5\sqrt{5}-2\sqrt{3}-2\sqrt{5}\right)\left(3\sqrt{5}-\sqrt{3}+3\sqrt{3}\right)\)

\(=\left(3\sqrt{5}-2\sqrt{3}\right)\left(3\sqrt{5}+2\sqrt{3}\right)\)

\(=\left(3\sqrt{5}\right)^2-\left(2\sqrt{3}\right)^2\)

\(=15-12\)

\(=3\)

bạn viết lại đề câu a.

b: 12/20+6/18=3/5+1/3=9/15+5/15=14/15

c: 8/12+20/30=2/3+2/3=4/3

d: 10/12+12/36=5/6+2/6=7/6