so sánh:
a,\(\dfrac{4}{9}vs\dfrac{13}{18}\) b,\(-\dfrac{15}{7}vs-\dfrac{6}{5}\) c,\(\dfrac{278}{37}vs\dfrac{287}{46}\) d,\(-\dfrac{157}{623}\)vs\(-\dfrac{47}{213}\)
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Những câu hỏi liên quan
BT
8 tháng 6 2017
Áp dụng 1.5 ta có:
a) \(\dfrac{4}{9}< 1\Rightarrow\dfrac{4}{9}< \dfrac{4+9}{9+9}=\dfrac{13}{18}\).
b) \(\dfrac{-15}{7}< 1\Rightarrow\dfrac{-15}{7}< \dfrac{-15+3}{7+3}=\dfrac{-12}{10}=\dfrac{-6}{5}\).
c) \(\dfrac{278}{37}>1\Rightarrow\dfrac{278}{37}>\dfrac{278+9}{37+9}=\dfrac{278}{46}\).
d) \(\dfrac{-157}{623}< 1\Rightarrow\dfrac{-157}{623}< \dfrac{-157+16}{623+16}=\dfrac{-141}{639}=\dfrac{-47}{213}\);
25 tháng 6 2017
a) \(\dfrac{4}{9}\)và \(\dfrac{13}{18}\)
Ta có : \(\dfrac{4}{9}\)=\(\dfrac{4.2}{9.2}\)=\(\dfrac{8}{18}\)
\(\Rightarrow\)\(\dfrac{8}{18}\)>\(\dfrac{13}{18}\)
giữ nguyên \(\dfrac{13}{18}\) (vì \(8>13\))
- Vậy \(\dfrac{4}{9}>\dfrac{13}{18}\)
b)\(-\dfrac{15}{7}\)và \(-\dfrac{6}{5}\)
Ta có :\(-\dfrac{15}{7}=\dfrac{-15.5}{7.5}=\dfrac{-75}{35}\)
\(\Rightarrow\)\(-\dfrac{75}{35}< \dfrac{-42}{35}\)
\(-\dfrac{6}{5}=\dfrac{-6.7}{5.7}=\dfrac{-42}{35}\) (vì - 75>-42)
- vậy \(\dfrac{-15}{7}< \dfrac{-6}{5}\)
c)\(\dfrac{278}{37}\)và \(\dfrac{287}{46}\)
Ta có :\(\dfrac{278}{37}=\dfrac{278.46}{37.46}=\dfrac{12788}{1702}\)
\(\Rightarrow\)\(\dfrac{12788}{1702}>\dfrac{10286}{1702}\)
\(\dfrac{287}{46}=\dfrac{287.37}{46.37}=\dfrac{10286}{1702}\) (vì 12788>10286)
- vậy \(\dfrac{278}{37}>\dfrac{10286}{46}\)
d)\(-\dfrac{157}{623}\)và \(-\dfrac{47}{213}\)
\(-\dfrac{157}{623}=\dfrac{-157.213}{623.213}=\dfrac{-33441}{132699}\)
\(\Rightarrow\dfrac{-33441}{132699}< \dfrac{-29281}{132699}\)
\(\dfrac{-47}{213}=\dfrac{-47.623}{213.623}=\dfrac{-29281}{132699}\) (vì -33441<-29281)
-vậy \(-\dfrac{157}{623}< -\dfrac{47}{213}\)
NT
5
8 tháng 6 2017
a, 4\9 < 13\18
b,-15\7 < -6\5
c,278\37 > 287\46
d,-157\623 < -47\213
24 tháng 3 2017
1/Ta co :
\(\dfrac{15}{7}.\left(\dfrac{1}{5}-\dfrac{46}{45}\right)+\dfrac{46}{45}.\left(\dfrac{15}{7}-\dfrac{45}{46}\right)\)
=\(\dfrac{15}{7}.\dfrac{1}{5}-\dfrac{15}{7}.\dfrac{46}{45}+\dfrac{46}{45}.\dfrac{15}{7}-\dfrac{46}{45}.\dfrac{45}{46}\)
=\(\dfrac{15}{7}.\left(\dfrac{1}{5}-\dfrac{46}{45}+\dfrac{46}{45}\right)-1\)
=\(\dfrac{15}{7}.\dfrac{1}{5}-1\)
=\(\dfrac{3}{7}-1=\dfrac{-4}{7}\)
2/Ta co
\(\dfrac{43}{47}.\left(\dfrac{18}{37}+\dfrac{47}{43}\right)-\dfrac{18}{3}.\left(\dfrac{43}{47}+\dfrac{37}{36}\right)\)
=\(\dfrac{43}{47}.\dfrac{18}{37}+\dfrac{43}{47}.\dfrac{47}{43}-\dfrac{18}{37}.\dfrac{43}{47}+\dfrac{18}{37}.\dfrac{37}{36}\)
=\(\dfrac{18}{37}.\left(\dfrac{43}{37}-\dfrac{43}{37}+\dfrac{37}{36}\right)+1\)
=\(\dfrac{18}{37}.\dfrac{37}{36}+1\)
=\(\dfrac{1}{2}+1=\dfrac{3}{2}\)
tick cho mk nha
H9
HT.Phong (9A5)
CTVHS
11 tháng 10 2023
a) \(\dfrac{6}{14}=\dfrac{6:2}{14:2}=\dfrac{3}{7}\)
\(\dfrac{3}{7}< \dfrac{4}{7}\)
b) \(\dfrac{6}{15}=\dfrac{6:3}{15:3}=\dfrac{2}{5}\)
\(\dfrac{3}{5}>\dfrac{2}{5}\)
c) \(\dfrac{10}{18}=\dfrac{10:2}{18:2}=\dfrac{5}{9}\)
\(\dfrac{5}{9}>\dfrac{2}{9}\)
21 tháng 4 2022
a. 7/9 - 16/9 = -9/9 = -1
b. 2/-15 + 7/10 = 17/30
c. (4 2/3 - 4 3/4) : -5/12 - 4/5
= (14/3 - 19/4) : (-5/12) - 4/5
= -1/12 : (-5/12) - 4/5
= 1/5 - 4/5
= -3/5
MN
9 tháng 5 2021
\(a.\)
\(-\dfrac{2}{9}+\dfrac{7}{-9}=\dfrac{-2}{9}-\dfrac{7}{9}=\dfrac{-2-7}{9}=\dfrac{-9}{9}=-1\)
\(b.\)
\(\dfrac{1}{-6}+\dfrac{13}{-15}=-\dfrac{1}{6}-\dfrac{13}{15}=\dfrac{\left(-1\right)\cdot5-13\cdot2}{30}=\dfrac{-5-26}{30}=\dfrac{-31}{30}\)
\(c.\)
\(\dfrac{5}{-6}+\dfrac{-5}{12}+\dfrac{7}{18}=\dfrac{-5}{6}-\dfrac{5}{12}+\dfrac{7}{18}=\dfrac{\left(-5\right)\cdot6-5\cdot3+7\cdot2}{36}=\dfrac{-31}{36}\)
9 tháng 5 2021
a) \(\dfrac{-2}{9}+\dfrac{7}{-9}=\dfrac{-2+-7}{9}=-1\)
b)\(\dfrac{1}{-6}+\dfrac{13}{-15}=\dfrac{-5}{30}+\dfrac{26}{30}=\dfrac{-5+26}{30}=\dfrac{7}{10}\)
c) \(\dfrac{5}{-6}+\dfrac{-5}{12}+\dfrac{7}{18}=\dfrac{-30}{36}+\dfrac{-15}{36}+\dfrac{18}{36}=\dfrac{-30+-15+18}{36}=\dfrac{-3}{4}\)
21 tháng 5 2021
a) \(x=\dfrac{-2}{7}+\dfrac{9}{7}=1\)
b) \(\dfrac{x}{3}=\dfrac{2}{5}+\dfrac{-4}{3}\)
\(\dfrac{x}{3}=\dfrac{-14}{15}\)
\(\Rightarrow x=\dfrac{3.-14}{15}=\dfrac{-14}{5}\)
21 tháng 5 2021
\(x=\dfrac{-2}{7}+\dfrac{9}{7}\)
\(x=1\)
31 tháng 7 2017
Trời ơi cái đề bài !!!
Thoy thì làm từng câu vậy
a) \(I=10101.\left(\dfrac{5}{111111}+\dfrac{5}{222222}-\dfrac{4}{111111}\right)\)
\(I=10101.\left(\dfrac{10}{222222}+\dfrac{5}{222222}-\dfrac{8}{222222}\right)\)
\(I=10101.\left(\dfrac{15}{222222}-\dfrac{8}{222222}\right)\)
\(I=10101.\dfrac{7}{222222}\)
\(I=\dfrac{7}{22}\)
a: 4/9=8/18<13/18
b: \(\dfrac{-15}{7}=\dfrac{-75}{35}\)
\(\dfrac{-6}{5}=\dfrac{-42}{35}\)
mà -75<-42
nên \(-\dfrac{15}{7}< -\dfrac{6}{5}\)
c: 37/278=1-241/278
46/287=1-241/287
mà 241/278>241/287
nên 37/278<46/287
=>278/37>286/47