ta có :
200410 + 20049 = 20049 . 2004 + 20049 . 1 = 20049 . ( 2004 + 1 ) = 20049 . 2005
200510 = 20059 . 2005
Vì 2004 < 2005 nên 20049 . 2005 < 20059 . 2005 hay 200410 + 20049 < 200510
Ta có 2004^10+2004^9=2004^9+(2004+1)=2004^9.2005
2005^10=2005^9.2005
vì 20049< 20059
suy ra 2004^10+2004^9< 2005^10