`4.`
Ta có :
`127/128 < 1`
`1345/1344 >1`
`=> 127/128 < 1345/1344`
`=> -127/128 > -1345/1344`
`=> x >y`
Vậy `x>y`
`5.`
Ta có :
`11/33 = 836/2508`
`25/76 = 825/2508`
`=> 11/33 > 25/76`
`=> -11/33 < -25/76`
`=> x < y`
Vậy `x<y`
`6.`
Ta có :
`2002/2003 < 1`
`14/13 >1`
`=> 14/13 > 2002/2003`
`=> x >y`
Vậy `x>y`