`(1999xx2000+2001xx5-5)/(504xx2000+500xx2000)`

`=(1999xx2000+5xx(2001-1))/(2000xx(504+500))`

`=(1999xx2000+5xx2000)/(2000xx1004)`

`=(2000xx(1999+5))/(2000xx1004)`

`=(2000xx2004)/(2000xx1004)`

`=2004/1004`

`=501/251`

$\color{red}{\text{@Hy~Hoctotnha}}$

Đáp án+Giải thích các bước giải:

`( 1999 xx 2000 + 2001 xx 5 - 5 )/( 504 xx 2000 + 500 xx 2000 )`

`= ( 1999 xx 2000 + 5 xx ( 2001 - 1 ) )/( 2000 xx ( 504 + 500 ))`

`= ( 1999 xx 2000 + 5 xx 2000 )/( 2000 xx 1004 )`

`= ( 2000 xx ( 1999 + 5 ))/( 2000 xx 1004 )`

`= 2004/1004`

`= 501/251`