Tham khảo:https://hoc24.vn/cau-hoi/cho-a-20213-va-b-202020212022-khong-tinh-cu-the-cac-gia-tri-cua-a-va-b-hay-so-sanh-a-va-b-ai-lam-giup-mik-voi.3007463332171

có sai ko bạn 

lúc mình làm xiong thấy sai

a>b, mik chắc luôn nhưng ko bt giải thích

A<B

A<B nhé

A < B 

\(A>\left(2021^2-1\right)\cdot2021=\left(2021-1\right)\left(2021+1\right)\cdot2021=B\)

\(A=2021^3=2021\cdot2021^2>2021\left(2021^2-1\right)=2021\left(2021\cdot2021-2021+2021-1\right)=2021\cdot\left(2021+1\right)\left(2021-1\right)=2021\cdot2022\cdot2020=B\)

\(B=2020.2021.2022=\left(2021-1\right).2021.\left(2021+1\right)=\left[\left(2021-1\right)\left(\left(2021+1\right)\right)\right].2011=\left(2021^2-1\right).2021=2021^3-2021< 2021^3=A\)

B = 2020.2021.2022

B = (2021 - 1).(2021 + 1).2021

B = (2021.2021 + 2021 - 2021 - 1).2021

B = (2021²⁰²¹-1).2021

B = 2021³ - 2021

Vậy A > B

2020.2022=(2021−1)(2021+1)=20212−1<\(2021^2\)

\(\Rightarrow2020.2021.2022< 2021^2.2021=2021^3\)

\(B=\left(2021-1\right)\left(2021+1\right).2021=\left(2021^2-1\right).2021=2021^3-2021< A\)

A = 2021^2*2021    B = (2021 - 1).(2021+1).2021

A=2021^2.2021      B = (2021^2-1)*2021(7 hằng đẳng thức đáng nhớ)

suy ra A > B