Đáp án:

 `a) (2008 × 2009 - 16)/(4000 + 2007 × 2008)`

`= (2008 × 2007 + 2008 × 2 - 16)/(2007 × 2008 + 4000)`

`= (2007 × 2008 + 4016 - 16)/(2007 × 2008 + 4000)`

`= (2007 × 2008 + 4000)/(2007 × 2008 + 4000)`

`= 1`

Vậy `(2008 × 2009 - 16)/(4000 + 2007 × 2008) = 1`

`b) (257 × 752 - 256)/(752 × 254 + 2000)`

`= (254 × 752 + 752 × 3 - 256)/( 254 ×752 + 2000)`

`= (254 × 752 + 2256 - 256)/(254 × 752 + 2000)`

`= (254 × 752 + 2000)/(254 × 752 + 2000)`

`= 1`

Vậy `(257 × 752 - 256)/(752 × 254 + 2000) = 1`

`c) (2007 × 2008 - 8)/(2000 + 2006 × 2008)`

`= (2006  × 2008 + 2008 - 8)/(2006 × 2008 + 2000)`

`= (2006 × 2008 + 2000)/(2006 × 2008 + 2000)`

`= 1`

Vậy `(2007 × 2008 - 8)/(2000 + 2006 × 2008) = 1`

Đáp án `+` Giải thích các bước giải:

a. `(2008xx2009-16) /(4000+ 2007 xx 2008`

`=> (4 034 072 -16)/(4000+2007xx2008`

`=> 4034056/(4000+ 2007 xx 2008`

`=> 4034056/(4000+ 4030056`

`=> 4034056/4034056`

`=> 1`

b.` (257xx 752-256)/( 2000+752xx 254)`

`=> (193264-256)/( 2000+752xx 254)`

`=> 193008/( 2000+752xx 254)`

`=> 193008/( 2000+191008)`

`=> 193008/193008`

`=> 1`

c.  `(2007xx2008-8) /(2000+2006xx 2008 `

`=> (4030056-8) /(2000+2006xx 2008`

`=> 4030048 /(2000+2006xx 2008`

`=> 4030048 /(2000+4028048`

`=> 4030048 /4030048`

`=> 1`