So sánh 9/15 và 7/2
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
Mẫu số chung 2 phân số: 84
\(\dfrac{3}{7}=\dfrac{3*12}{7*12}=\dfrac{36}{84}\)
\(\dfrac{5}{12}=\dfrac{5*7}{12*7}=\dfrac{35}{84}\)
Vì \(36>35\) nên\(\dfrac{36}{84}>\dfrac{35}{84}\)
Vậy \(\dfrac{3}{7}>\dfrac{5}{12}\)
Ta có:
\(\dfrac{9}{8}>1>\dfrac{2023}{2024}\) nên \(\dfrac{9}{8}>\dfrac{2023}{2024}\)
Ta có:
\(\dfrac{1+15}{16}=1\)
\(\dfrac{1+16}{15}=\dfrac{17}{15}>1\)
\(\Rightarrow\dfrac{1+15}{16}>\dfrac{1+16}{15}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a. 6/7 = 6x9/7x9=54/63
7/9=7x7/9x7=49/63
do 54/73>49/63 => 6/7>7/9
b.8/11=8x9/11x9=72/99
15/9=15x11/9x11=165/99
do 72/99<165/99=>8/11<15/9
![](https://rs.olm.vn/images/avt/0.png?1311)
a: 6^9=(6^3)^3=216^3>15^3
B: 6^36=(6^2)^18=36^18>35^18
c: 7^18=(7^2)^9=49^9>30^9
d: 3^500=243^100
7^300=343^100
=>3^500<7^300
![](https://rs.olm.vn/images/avt/0.png?1311)
a: \(0.2=\dfrac{2}{10}\)
10>7
=>\(\dfrac{2}{10}< \dfrac{2}{7}\)
=>\(\dfrac{2}{7}>0.2\)
b: \(-\dfrac{1^5}{6}=\dfrac{-1}{6}=\dfrac{-3}{18}\)
\(\dfrac{8}{-9}=-\dfrac{16}{18}\)
mà -3>-16
nên \(-\dfrac{1^5}{6}>\dfrac{8}{-9}\)
c: \(\dfrac{2017}{2016}>1\)
\(1>\dfrac{2017}{2018}\)
Do đó: \(\dfrac{2017}{2016}>\dfrac{2017}{2018}\)
d: \(-\dfrac{249}{333}=\dfrac{-249:3}{333:3}=\dfrac{-83}{111}\)
e: \(\dfrac{5^1}{3}=\dfrac{5}{3}=\dfrac{15}{9}\)
\(\dfrac{4^8}{9}=\dfrac{65536}{9}\)
mà 15<65536
nên \(\dfrac{5^1}{3}< \dfrac{4^8}{9}\)
f: 13,589<13,612
![](https://rs.olm.vn/images/avt/0.png?1311)
\(-\dfrac{4}{5};\dfrac{6}{7}\)
Có \(MSC=35\)
\(-\dfrac{4}{5}=\dfrac{-4\times7}{5\times7}=-\dfrac{28}{35}\)
\(\dfrac{6}{7}=\dfrac{6\times5}{7\times5}=\dfrac{30}{35}\)
So sánh :
\(-\dfrac{3}{7}=-0,43;\dfrac{4}{-9}=-0,44;\dfrac{25}{-15}=-1,66\)
\(\Rightarrow\dfrac{25}{-15}>\dfrac{4}{-9}>-\dfrac{3}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Đơn giản
Ta thấy :
9/15 <1
7/2 > 1
vậy 9/15 < 7/2
9/15=18/30
7/2=105/30
vì 18/30<105/30 nên 9/15<7/2