So Sánh: A= \(\frac{2000^{2001}+1}{2000^{2002}+1}\) và B= \(\frac{2000^{2000}+1}{2000^{2001}+1}\)
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
B = \(\frac{2000}{2001+2002}\)+ \(\frac{2001}{2001+2002}\)
Vì \(\frac{2000}{2001}\)> \(\frac{2000}{2001+2002}\)
\(\frac{2001}{2002}\)> \(\frac{2001}{2001+2002}\)
=> \(\left(\frac{2000}{2001}+\frac{2001}{2002}\right)\)> \(\left(\frac{2000}{2001+2002}+\frac{2001}{2001+2001}\right)\)
=> A>B
Vậy A>B
![](https://rs.olm.vn/images/avt/0.png?1311)
có:A=2000^2001+1/2000^2002+1
=)2000A=2000^2002+2000/2000^2002+1=2000^2002+1+1999/2000^2002+1
=1999/2000^2002+1
lại có:B=2000^2000+1/2000^2001+1
=)2000B=2000^2001+2000/2000^2001+1=2000^2001+1+1999/2000^2001+1
=1999/2000^2001+1
vì 1999/2000^2002+1 < 1999/2000^2001+1
=)2000A < 2000B hay A<B
![](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)
Ta có: \(\frac{1999x2000}{1999x2000+1}=\frac{1999x2000+1-1}{1999x2000+1}=1-\frac{1}{1999x2000+1}\)
\(\frac{2000x2001}{2000x2001+1}=\frac{2000x2001+1-1}{2000x2001+1}=1-\frac{1}{2000x2001+1}\)
Nhận thấy: \(\frac{1}{1999x2000+1}>\frac{1}{2000x2001+1}\)=> \(1-\frac{1}{1999x2000+1}< 1-\frac{1}{2000x2001+1}\)
=> \(\frac{1999x2000}{1999x2000+1}=\frac{2000x2001}{2000x2001+1}\)
\(\frac{1999x2000}{1999x2000+1}< \frac{2000x2001}{2000x2001+1}\)
![](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)
A = \(\frac{2000+2001}{2001+2002}\)= \(\frac{4001}{4003}\)
B = \(\frac{2000+2001}{2001+2003}=\frac{4001}{4003}\)
vậy A = B
![](https://rs.olm.vn/images/avt/0.png?1311)
ta có:\(A=\frac{2000}{2001}+\frac{2001}{2002}<\frac{2000}{2002}+\frac{2001}{2002}=\frac{2000+2001}{2002}<\frac{2000+2001}{2001+2002}=B\)
\(\Rightarrow A
ta có:\(B=\frac{2000+2001}{2001+2002}=\frac{2000}{2001+2002}+\frac{2001}{2001+2002}\)
vì \(\frac{2000}{2001}>\frac{2000}{2001+2002}và\frac{2001}{2002}>\frac{2001}{2001+2002}\)
\(\Rightarrow\frac{2000}{2001}+\frac{2001}{2002}>\frac{2000+2001}{2001+2002}\)
=>A>B
![](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
A<B
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