Bài 92
a ) Ta có :
`2007/2008 = 1 - 1/2008`
`2008/2009 = 1 - 1/2009`
Vì `1/2008 > 1/2009` nên `2007/2008 > 2008/2009`
b ) Ta có :
`2/3 = 1 - 1/3`
`3/4 = 1 - 1/4`
Vì `1/3 > 1/4` nên `2/3 > 3/4`
c ) Ta có :
`2/13 = 1 - 11/13`
`3/14 = 1 - 11/14`
Vì `11/13 > 11/14` nên `2/13 > 3/14`
d ) Ta có :
`5/14 = 1 - 9/14`
`2/11 - 1 - 9/11`
Vì `9/14 < 9/11` nên `5/14 < 2/11`
e ) Ta có :
`5/6 = 1 - 1/6`
`9/10 = 1 - 1/10`
Vì `1/6 > 1/10` nên `5/6 > 9/10`
f ) Ta có :
`77/78 = 1 - 1/78`
`78/79 = 1 - 1/79`
Vì `1/78 > 1/79` nên `77/78 > 78/79`
Bài 93
`a ) 77/99 = {77 : 11}/{99 : 11} = 7/9`
`777/999 = {777 : 111}/{999 : 111} = 7/9`
`7/9 = 7/9 = 7/9 => 7/9 = 77/99 = 777/999`
`b ) 123123/127127 = {123123 : 1001}/{127127 : 1001} = 123/127`
`123/127 = 123/127 => 123/127 = 123123/127127`
`c ) 1313/1515 = {1313 : 101}/{15 : 101} = 13/15`
`131313/151515 = {131313 : 10101}/{151515 : 10101} = 13/15`
`13/15 = 13/15 = 13/15 => 13/15 = 1313/1515 = 131313/151515`
`#dtkc`
