Question

Tính giá trị biểu thức: A=\(\frac{2020}{2019}-\frac{2019}{2018}+\frac{1}{2018\times2019}\)

Answer 1

\(A=\frac{2020}{2019}-\frac{2019}{2018}+\frac{1}{2019\times2018}\)

\(=\frac{2020\times2018}{2019\times2018}-\frac{2019\times2019}{2019\times2018}+\frac{1}{2019\times2018}\)

\(=\frac{2020\times2018-2019\times2019+1}{2019\times2018}\)

\(=\frac{\left(2019+1\right)\times\left(2019-1\right)-2019\times2019+1}{2019\times2018}\)

\(=\frac{2019\times2019-2019+2019-1-2019\times2019+1}{2019\times2018}\)

\(=\frac{2019\times2019-1-\left(2019\times2019-1\right)}{2019\times2018}\)

\(=\frac{0}{2019\times2018}\)

\(=0\)

Vậy A = 0 

Answer 2

ta có

A=2020*2018/2019*2018-2019*2019/2018*2019+1/2018*2019

=>A*(2018*2019)=2020*2018-2019*2019+1

=>A*(2018*2019)=(2019+1)*2018-(2018+1)*2019+1

=>A*(2018*2019)=(2019*2018+2018)-(2018*2019+2019)+1

=>A*(2018*2019)=2019*2018+2018-2018*2019-2019+1

=>A*(2018*2019)=2018-2019+1

=>A*(2018*2019)=2018+1-2019

=>A*(2018*2019)=0

=>A=0/(2018*2019)

=>A=0