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Ta có : \(\frac{17}{-5}=-1-\frac{12}{5}\)
\(-\frac{6}{5}=-1-\frac{1}{5}\)
Mà : 1/5 < 12/5
=> \(\frac{-6}{5}>\frac{-15}{7}\)
278/37=7+19/37
287/46=6+11/46
Vì 7+19/37>6+11/46
=>278/37>287/46
k mình nha Nguyễn Thanh Thư
278/37=7+19/37
287/46=6+11/46
Vì 7+19/37>6+11/46
=>278/37>287/46
a) \(\frac{278}{37}\) và \(\frac{287}{46}\)
Vì \(37< 46\) nên \(\frac{278}{37}>\frac{287}{46}\)
b) \(\frac{547}{216}\) và \(\frac{546}{215}\)
Ta có:
\(\frac{547}{216}-2=\frac{115}{216}\)
\(\frac{546}{215}-2=\frac{116}{215}\)
Vì \(\frac{115}{216}< \frac{116}{215}\) nên \(\frac{547}{216}< \frac{546}{215}\)
a) \(\frac{278}{37}=7+\frac{19}{37}\) \(\frac{287}{46}=7-\frac{35}{46}\)
\(\frac{278}{37}>7>\frac{287}{46}\Rightarrow\frac{278}{37}>\frac{287}{46}\)
b) Ta có: \(\frac{547}{216}=1+\frac{331}{216}\)
\(\frac{546}{215}=1+\frac{331}{215}\)
mà \(\frac{331}{216}< \frac{331}{215}\)
=> \(\frac{547}{216}< \frac{546}{215}\)
Ta có:\(\frac{-157}{623}=\frac{-331441}{132699}\)
\(\frac{-47}{213}=\frac{-29281}{132699}\)
Vì \(-331441< -29281\)nên\(\frac{-331441}{132699}< \frac{-29281}{132699}\)
hay\(\frac{-157}{623}< \frac{-47}{213}\)
Vậy \(\frac{-157}{623}< \frac{-47}{213}\)
Để dễ hơn ta so sánh \(\frac{157}{623}\)và \(\frac{47}{213}\)
Ta có \(\frac{47}{213}=\frac{141}{639}\)
Ta có \(\frac{157}{623}=\frac{780}{623}-1;\frac{141}{639}=\frac{780}{639}-1\)
Mà \(\frac{780}{623}>\frac{780}{639}\)=) \(\frac{780}{623}-1>\frac{780}{639}-1\)
=) \(\frac{157}{623}>\frac{141}{639}=\frac{47}{213}\)=) \(\frac{-157}{623}< \frac{-47}{213}\)
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) \(\dfrac{-157}{623}< 1\Rightarrow\dfrac{-157}{623}< \dfrac{-157+16}{623+16}=\dfrac{-141}{639}=\dfrac{-47}{213}\);
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 \(-\dfrac{157}{623}< -\dfrac{47}{213}\)
a) ta có : 1-278/37= -241/37
1-287/46= -241/46
Vì -241/37>-241/46 <=> 278/37>287/46