a) \(< \)

b) \(>\)

c) \(< \)

d) \(>\)

e) \(< \)

g) \(>\)

h) \(>\)

k) \(>\)

\(7\dfrac{4}{5}và9\dfrac{1}{2}\\ Tacó:7< 9\\ \Rightarrow7\dfrac{4}{5}< 9\dfrac{1}{2}\\ 7\dfrac{1}{6}và3\dfrac{4}{5}\\ Tacó:7>3\\ \Rightarrow7\dfrac{1}{6}>3\dfrac{4}{5}\)

Câu cuối không phải hỗn số

`a)1<3`

`=>1/5<3/5`

`b)21>9`

`=>8/21<8/9`

`c)3/5<5/5=1`

`d)7/5>5/5=1`

a)3/5>1/5 b)8/21<8/9 c)3/5<1 d)7/5>1

a 1/5<3/5

b 8/21<8/9

c 3/5<1

d 7/5>1

58<8558...85

\(\dfrac{1}{4}< \dfrac{1}{9}\)

>;<

a: \(\dfrac{-7}{6}=\dfrac{-7\cdot3}{6\cdot3}=\dfrac{-21}{18}\)

\(\dfrac{-11}{9}=\dfrac{-11\cdot2}{9\cdot2}=\dfrac{-22}{18}\)

mà -21>-22

nên \(-\dfrac{7}{6}>-\dfrac{11}{9}\)

b: \(\dfrac{5}{-7}=\dfrac{-5}{7}=\dfrac{-5\cdot5}{7\cdot5}=\dfrac{-25}{35}\)

\(\dfrac{-4}{5}=\dfrac{-4\cdot7}{5\cdot7}=\dfrac{-28}{35}\)

mà -25>-28

nên \(\dfrac{5}{-7}>\dfrac{-4}{5}\)

c: \(\dfrac{-8}{7}< -1\)

\(-1< -\dfrac{2}{5}\)

Do đó: \(-\dfrac{8}{7}< -\dfrac{2}{5}\)

d: \(-\dfrac{2}{5}< 0\)

\(0< \dfrac{1}{3}\)

Do đó: \(-\dfrac{2}{5}< \dfrac{1}{3}\)

\(S=\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{10}+\dfrac{1}{41}+\dfrac{1}{42}\)

Ta có :

+) \(\dfrac{1}{9}+\dfrac{1}{10}< \dfrac{1}{8}+\dfrac{1}{8}\)

+) \(\dfrac{1}{41}+\dfrac{1}{42}< \dfrac{1}{40}+\dfrac{1}{40}\)

\(\Leftrightarrow S< \dfrac{1}{5}+\dfrac{1}{8}+\dfrac{1}{8}+\dfrac{1}{40}+\dfrac{1}{40}\)

\(\Leftrightarrow S< \dfrac{1}{2}\)

Vậy,,,

Ta có: \(\dfrac{1}{9}+\dfrac{1}{10}< \dfrac{1}{8}+\dfrac{1}{8}=\dfrac{2}{8}=\dfrac{1}{4}\)

\(\dfrac{1}{41}+\dfrac{1}{42}< \dfrac{1}{40}+\dfrac{1}{40}=\dfrac{2}{40}=\dfrac{1}{20}\)

Do đó: \(\dfrac{1}{9}+\dfrac{1}{10}+\dfrac{1}{41}+\dfrac{1}{42}< \dfrac{1}{4}+\dfrac{1}{20}=\dfrac{6}{20}=\dfrac{3}{10}\)

\(\Leftrightarrow\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{10}+\dfrac{1}{41}+\dfrac{1}{42}< \dfrac{3}{10}+\dfrac{1}{5}=\dfrac{3}{10}+\dfrac{2}{10}=\dfrac{1}{2}\)

hay \(S< \dfrac{1}{2}\)(đpcm)

em trả lời ccaua này hi vọng thầy còn nhớ em

a) -9/4<`1/3

c) 9/-5<7/-10

a) \(\dfrac{-9}{4}< 0\)

\(0< \dfrac{1}{3}\)

Do đó: \(\dfrac{-9}{4}< \dfrac{1}{3}\)

đề bài là so sánh à bạn?

đề bài

a) \(\dfrac{1}{3}=\dfrac{1.5}{3.5}=\dfrac{5}{15}\)     

\(\dfrac{2}{5}=\dfrac{2.3}{5.3}=\dfrac{6}{15}\)

Vậy quy đồng mẫu số hai phân số 1/3 và 2/5 ta được 5/15 và 6/15

b)\(\dfrac{3}{7}=\dfrac{3.9}{7.9}=\dfrac{27}{63}\)

\(\dfrac{8}{9}=\dfrac{8.7}{9.7}=\dfrac{56}{63}\)

Vậy...

c)\(\dfrac{3}{5}=\dfrac{3.2}{5.2}=\dfrac{6}{10}\) giữ nguyên phân số 7/10

d)\(\dfrac{1}{3}=\dfrac{1.2}{3.2}=\dfrac{2}{6}\) giữ nguyên phân số 5/6