Câu 1.

$\frac{1}{15}-\frac{9}{15}=\frac{-8}{15}$

$\frac{2}{15}-\frac{10}{15}=\frac{-8}{15}$

$\frac{3}{15}-\frac{11}{15}=\frac{-8}{15}$

Câu 2:

$\frac{-9}{15}+\frac{1}{15}=\frac{-8}{15}$

$\frac{-10}{15}+\frac{2}{15}=\frac{-8}{15}$

$\frac{-11}{15}+\frac{3}{15}=\frac{-8}{15}$

các bạn giúp mk vs mk cần gấp!

a) 3/8 = 1/8 + 2/8 = 1/8 + 1/4

3/8 = 5/8 - 2/8 = 5/8 - 1/4

b) 5/12 = 1/12 + 4/12 = 1/12 + 1/3

5/12 = 7/12 - 2/12 = 7/12 - 1/6

c) 1/11 = -2/11 + 3/11

1/11 = 2/11 - 1/11

d) 1/4 = -2/4 + 3/4 = -1/2 + 3/4

1/4 = 5/4 - 4/4 = 5/4 -1

Ta có:

\(\dfrac{-1}{3}=\dfrac{-60}{120};\dfrac{-1}{4}=\dfrac{-30}{120}\)

=> ba số hữu tỉ xem giữa số \(\dfrac{-60}{120}\) và \(\dfrac{-30}{120}\)

=> Ba số hữu tỉ là: \(\dfrac{-40}{120};\dfrac{-45}{120};\dfrac{-55}{120}\)

Chúc bạn học tốt!!!

Ta có :

\(-\dfrac{1}{3}=-\dfrac{16}{48}\)

\(-\dfrac{1}{4}=-\dfrac{12}{48}\)

\(-\dfrac{16}{48}< -\dfrac{15}{48}< -\dfrac{14}{48}< -\dfrac{13}{48}< -\dfrac{12}{48}\)

Vậy 3 số hữu tỉ xen giữa \(-\dfrac{1}{3}\) và \(-\dfrac{1}{4}\) là : \(-\dfrac{15}{48};-\dfrac{14}{48};-\dfrac{13}{48}\)

\(\dfrac{-1}{2}=\dfrac{-1.12}{2.12}=\dfrac{-12}{24}\)

\(\dfrac{-1}{3}=\dfrac{-1.8}{3.8}=\dfrac{-8}{24}\)

Gọi các tỷ số đó là a

\(\dfrac{-12}{24}< a< \dfrac{-8}{24}\)

\(a\in\left\{\dfrac{-9}{24};\dfrac{-10}{24};\dfrac{-11}{24}\right\}\)

\(\dfrac{-1}{2}=-0,5\)

\(\dfrac{-1}{3}=-0,\left(3\right)\)

Suy ra \(-0,5< ...;...;...;< -0,\left(3\right)\)

\(\Rightarrow-0,5< -0,45< -0,44< -0,43< -0,\left(3\right)\)

\(\Rightarrow\dfrac{-1}{2}< \dfrac{-9}{20}< \dfrac{-11}{25}< \dfrac{-43}{100}< \dfrac{-1}{3}\)

Bài 1:

1)mik ko biết trục số ở đâu nên tham khảo:

2

-0,75 <5/3

a) \(\dfrac{-7}{20}=\dfrac{1}{5}.\dfrac{-7}{4}\) b) \(\dfrac{-7}{20}=\dfrac{-7}{40}:\dfrac{1}{2}\) c) \(\dfrac{-7}{20}=\dfrac{2}{5}+\dfrac{-3}{4}\) d) \(\dfrac{-7}{20}=\dfrac{-1}{5}+\dfrac{-3}{20}\)

a)\(\dfrac{-7}{20}=\dfrac{-7}{10}\times\dfrac{1}{2}\)

b)\(\dfrac{-7}{20}=\dfrac{-7}{40}\times\dfrac{1}{2}\)

c)\(\dfrac{-7}{20}=\dfrac{7}{20}+\dfrac{-7}{10}\)

d)\(\dfrac{-7}{20}=\dfrac{-1}{5}+\dfrac{-3}{20}\)

a) \(3,7:4,5=\dfrac{3,7}{4,5}=\dfrac{37}{45}\)

b) \(2\dfrac{1}{3}:4\dfrac{2}{3}=\dfrac{7}{3}:\dfrac{14}{3}=\dfrac{7}{3}\times\dfrac{3}{14}=\dfrac{1}{2}\)

c) \(\dfrac{3}{8}:0,7=\dfrac{3}{8}:\dfrac{7}{10}=\dfrac{3}{8}\times\dfrac{10}{7}=\dfrac{15}{28}\)

d) \(5\dfrac{1}{7}:2\dfrac{1}{3}=\dfrac{36}{7}:\dfrac{7}{3}=\dfrac{36}{7}\times\dfrac{3}{7}=\dfrac{108}{49}\)

cảm ơn bạn

Ba số hữu tỉ đó có dạng \(\dfrac{x}{y}\) với x; y ∈ Z, y ≠ 0

Theo bài ra: \(\dfrac{-1}{100}< \dfrac{x}{y}< \dfrac{1}{100}\)

⇒ \(\dfrac{-2}{200}< \dfrac{x}{y}< \dfrac{2}{200}\)

⇒ \(\dfrac{x}{y}\) ∈ \(\)\(\left\{-\dfrac{1}{200};0;\dfrac{1}{200};\right\}\)

Vậy ba số hữu tỉ cần tìm là: \(\dfrac{-1}{200};0;\dfrac{1}{200}\)

thanks