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ta có:19/20<20/20 và 20/20<20/21
ta có:1-17/21=21/21-17/21=4/21
nên 4/21>4/27
1-23/27=27/27=4/27
ta có:31/29-1=31/29-29/29=2/29
nên 31/29>45/43
45/43-1=43/43-45/43=2/43
nhớ k mình nha
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Ta có cách:
1 - 12/13 = 1/13
1 - 13/14 = 1/14
Vì 1/13 < 1/14 nên => 1/13 > 1/14
tk mk nha nếu đúng
Ta có:\(1-\frac{12}{13}=\frac{1}{13}\)
\(1-\frac{13}{14}=\frac{1}{14}\)
Mà \(\frac{1}{14}< \frac{1}{13}\).Vì số trừ càng lớn thì hiệu càng nhỏ
\(\Rightarrow\frac{12}{13}< \frac{13}{14}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
A) Ta có:
\(\dfrac{12}{13}=\dfrac{13}{13}-\dfrac{1}{13}=1-\dfrac{1}{13}\)
\(\dfrac{13}{14}=\dfrac{14}{14}-\dfrac{1}{14}=1-\dfrac{1}{14}\)
Mà \(1-\dfrac{1}{13}< -\dfrac{1}{14}\)
\(\Rightarrow\dfrac{12}{13}< \dfrac{13}{14}\)
B) Ta có:
\(\dfrac{125}{251}=\dfrac{251}{251}-\dfrac{126}{251}=1-\dfrac{126}{251}\)
\(\dfrac{127}{253}=\dfrac{253}{253}-\dfrac{126}{253}=1-\dfrac{126}{253}\)
Mà: \(1-\dfrac{126}{251}< 1-\dfrac{126}{253}\)
\(\Rightarrow\dfrac{125}{251}< \dfrac{127}{253}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta thấy : \(1-\frac{12}{13}=\frac{1}{13}\)
\(1-\frac{13}{14}=\frac{1}{14}\)
Mà \(\frac{1}{13}>\frac{1}{14}\) nên \(\Rightarrow\frac{12}{13}< \frac{13}{14}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) có 12/48 < 13/48, 13/48 < 13/47 => 12/48 < 13/47 b) có 415/395 > 1 , 572/581 <1 => 415/395 > 572/581
13 x 64 = 832
38 x 21 = 798
Do đó: 13 x 64 > 38 x 21
=> 13 x 64 x 1/64 x 1/38 > 38 x 21 x 1/64 x 1/38
=> 13/38 > 21/64
Ta có :
\(\frac{13}{38}>\frac{13}{39}\left(38< 39\right)\)
\(\Rightarrow\frac{13}{38}>\frac{1}{3}\left(1\right)\)
\(\frac{21}{64}< \frac{21}{63}\left(64>63\right)\)
\(\Rightarrow\frac{21}{64}< \frac{1}{3}\left(2\right)\)
Từ \(\left(1\right);\left(2\right)\)
\(\Rightarrow\frac{21}{64}< \frac{1}{3}< \frac{13}{38}\)
\(\Rightarrow\frac{21}{64}< \frac{13}{38}\)
Vậy \(\frac{21}{64}< \frac{13}{38}\)
~ Ủng hộ nhé