Đáp án:
Ta có: `2006 × 2007 - 2005`
`= 2006 × (2005 + 2) - 2005`
`= 2006 × 2005 + 2006 × 2 - 2005`
`= 2006 × 2005 + 4012 - 2005`
`= 2006 × 2005 + 2007`
`⇒ (2005 × 2006 + 2007) : (2006 × 2007 - 2005)`
`= (2005 × 2006 + 2007) : (2006 × 2005+ 2007)`
`= 1`