Question

简便方法计算:2004.05x1997.05-2001.05x1999.05 怎么算，真不知道怎么算，急要答案

Answer 1

先把式子简化成：
（2000+4.05）x(2000-2.95)-(2000+1.05)x(2000-0.95)
=2000x2000-2000x2.95+2000x4.05-4.05x2.95-{2000x2000-0.95x2000+1.05x2000-1.05x0.95}
= -2000x2.95+0.95x2000+2000x4.05-1.05x2000+1.05x0.95-4.05x2.95
= -2000x2-2000x0.95+0.95x2000+3x2000+1.05x0.95-{(3+1.05)x(2+0.95)}
= -4000+6000+1.05x0.95-{6+3x0.95+2x1.05+1.05x0.95}
=2000+1.05x0.95-6-3x0.95-2x1.05-1.05x0.95
=1994-4.95
=1989.05

Answer 2

=(2001+3.5)(2001-3.5)-(2001+0.5)(2001-1.5)
=2001^2-3.5^2-2001^2+2001+0.5*1.5
=2001-12.25-0.75
=1989.5

Answer 3

令2001.05=a
(a+3)(a-4)-a(a-2)
=a*a-a-12-a*a+2a
=a-12
=2001.05-12
=1989.05