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a) \(\frac{3}{-4}=\frac{-3}{4};\frac{-1}{-4}=\frac{1}{4}\)
Vì - 3 < 1 nên \(\frac{-3}{4}< \frac{1}{4}\)
hay \(\frac{3}{-4}< \frac{-1}{-4}\)
Quy đồng mẫu ta được:
15/17=15.27/17.27=405/459
25/27=25.17/27.27=425/459
⇒405/459<425/459⇒15/17<25/27
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: B = \(\frac{2000+2001}{2001+2002}=\frac{2000}{2001+2002}+\frac{2001}{2001+2002}=\frac{2000}{4003}+\frac{2001}{4003}\)
Ta thấy : \(\frac{2000}{2001}>\frac{2000}{4003}\)(1)
\(\frac{2001}{2002}>\frac{2001}{4003}\) (2)
Từ (1) và (2) cộng vế với vế, ta được :
\(\frac{2000}{2001}+\frac{2001}{2002}>\frac{2000}{4003}+\frac{2001}{4003}\)
hay \(A=\frac{2000}{2001}+\frac{2001}{2002}>B=\frac{2000+2001}{2001+2002}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
B=2000/2001+2002 + 2001/2001+2002
Ta có:2000/2001 > 2000/2001+2002
2001/2002 > 2001/2001+2002
Vậy A >B
![](https://rs.olm.vn/images/avt/0.png?1311)
Xét B=\(\frac{2000+2001}{2001+2002}\)\(=\)\(\frac{2000}{2001+2002}\)\(+\)\(\frac{2001}{2001+2002}\)
Mà \(\frac{2000}{2001}>\frac{2000}{2001+2002}\); \(\frac{2001}{2002}>\frac{2001}{2001+2002}\) \(\Rightarrow\)\(\frac{2000}{2001}+\frac{2001}{2002}\)\(>\frac{2000+2001}{2001+2002}\)
Vậy \(A>B\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:\(B=\frac{2000}{2001+2002}+\frac{2001}{2001-2002}\)
Vì:\(\frac{2000}{2001}>\frac{2000}{2001+2002}\)
\(\frac{2001}{2002}>\frac{2001}{2001+2002}\)
\(\Rightarrow\left(\frac{2000}{2001}+\frac{2001}{2002}\right)>\left(\frac{2000}{2001-2002}-\frac{2001}{2001+2001}\right)\)
\(\Rightarrow A>B\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta xét các phân số trong 2 biểu thức đều bằng nhau :
2000 = 2000 ; 2001 = 2001 ; 2002 = 2002.
Vậy A = B.
![](https://rs.olm.vn/images/avt/0.png?1311)
A = \(\frac{2000+2001}{2001+2002}\)= \(\frac{4001}{4003}\)
B = \(\frac{2000+2001}{2001+2003}=\frac{4001}{4003}\)
vậy A = B
Ta có:
B = \(\frac{2000}{2001+2002}\)+ \(\frac{2001}{2001+2002}\)
Vì \(\frac{2000}{2001}\)> \(\frac{2000}{2001+2002}\)
\(\frac{2001}{2002}\)> \(\frac{2001}{2001+2002}\)
=> \(\left(\frac{2000}{2001}+\frac{2001}{2002}\right)\)> \(\left(\frac{2000}{2001+2002}+\frac{2001}{2001+2001}\right)\)
=> A>B
Vậy A>B