2005+2005的平方-2005x2006
=2005x(1+2005-2006)
=2005x0
=0
58.4x1.4+18.6x58.4-20x18.4
=58.4x(1.4+18.6)-20x18.4
=58.4x20-20x18.4
=20x(58.4-18.4)
=20x40
=800
写得特别详细了..你可以自己把不必要的省略~