`a)` Ta có `: 1717/8585 = ( 1717 : 1717 )/( 8585 : 1717 ) = 1/5`
`1313/5151 = ( 1313 : 101 )/( 5151 : 101 ) = 13/51`
Vì `1/5 = 13/65 > 13/51` nên `1717/8585 > 1313/5151`
Vậy `, 1717/8585 > 1313/5151 .`
`b ) 9^8 . 5^16 = ( 3^2 )^8 . 5^16 = 3^16 . 5^16 = ( 3 . 5 )^16 = 15^16`
Vì `19^20 > 15^16` nên `19^20 > 9^8 . 5^16`
Vậy `, 19^20 > 9^8 . 5^16 .`