2005 × 2005 - 4010 × 2006 + 2006 × 2006
= 2005² - 2 × 2005 × 2006 + 2006²
= (2005 - 2006)²
= (-1)²
= 12005² - 2 × 2005 × 2006 + 2006²这一步是怎样转换到(2005 - 2006)²的呢？求大神详细点啊完全平方公式 (a - b)² = a² - 2ab + b²这题反过来看， a² - 2ab + b² = (a - b)²