Question

2019/2020-2018/2019怎样巧算？

Answer 1

2019/2020-2018/2019
=1-2018/2019-1/2020
=1/2019-1/2020
=（2020-2019）/4078380
=1/4078380
可以通过上面的巧算得到答案是1/4078380。

Answer 2

原式=(1-1/2020)-(1-1/2019)
=1-1/2020-1+1/2019
=1/2019-1/2020
=1/(2019×2020)

Answer 3

2019/2020-2018/2019
=1-1/2020-（1-1/2019）
=1/2019-1/2020
=1/4078380

Answer 4

2019/2020-2018/2019=(2019×2019)/(2020×2019)-(2018×2020)/(2020×2019)=(2019×2019)/(2020×2019)-[(2019-1)(2019+1)]/(2020×2019)=(2019×2019)/(2020×2019)-(2019×2019-1)/(2020×2019)=1/(2020×2019)。