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Giải:
a) 2019 + 2021 - 1
= 4040 - 1
= 4039
b) 2020 x 2019 + 2018
= 4078380 + 2018
= 4080398
Học tốt!!!
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=2018\times2020+2021\) và \(B=2019\times2019+2021\)
\(A=2018\times2019+2018+2021\)
\(B=2018\times2019+2019+2021\)
Vì \(2019>2018\Rightarrow A< B\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{2020}{2019}-\dfrac{2019}{2018}+\dfrac{1}{2019}x2018\)
\(=\dfrac{2020}{2019}-\dfrac{2019}{2018}+\dfrac{2018}{2019}=2-\dfrac{2019}{2018}=\dfrac{2017}{2018}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
2020 × 2021 - 1000 - 2020 × 2019 - 1020
= 2020 × 2021 - 2020 × 2019 - 1000 - 1020
= 2020 × 2021 - 2020 × 2019 - (1000 + 1020)
= 2020 × 2021 - 2020 × 2019 - 2020
= 2020 × 2021 - 2020 × 2019 - 2020 × 1
= 2020 × (2021 - 2019 - 1)
= 2020 × 1
= 2020.
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời :...............................................
\(\frac{4078379}{4078379}\)
Hk tốt,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
k nhé Kim Râu La
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời:
\(A=\frac{2}{2018.2020}+\frac{2021}{2020}-\frac{2020}{2019}\)
\(A=\frac{1}{2018}-\frac{1}{2020}+1+\frac{1}{2020}-\left(1+\frac{1}{2018}\right)\)
\(A=\frac{1}{2018}-\frac{1}{2020}+1+\frac{1}{2020}-1-\frac{1}{2018}\)
\(A=0\)
\(A=\frac{2}{2018}\cdot2020+\frac{2021}{2020}-\frac{2019}{2018}\)
\(A=\frac{2\cdot2020-2019}{2018}+\frac{2021}{2020}\)
\(A=\frac{2021}{2018}+\frac{2021}{2020}\)
\(A=\frac{2021\cdot\left(2020+2018\right)}{2018\cdot2020}=\frac{2021\cdot4038}{2018\cdot2020}=\frac{2021\cdot2019\cdot2}{2018\cdot1010\cdot2}=\frac{2020^2-1}{2018\cdot101\cdot10}\)
\(A=\frac{4080399}{20200180}\)
Cách giải đoàng hoàng nha !
2019 x ( 2021 - 1) 2019 x 2020 1 1
_______________ = ________________ = ___ = ______
2018 + 2019 x 2020 2018 + 2019 x 2020 2018 + 1 2019