https://olm.vn/hoi-dap/question/102758.html

a 

\(B=2020^2=2020^2-1^2+1^2=\left(2020-1\right)\left(2020+1\right)+1=2019\cdot2021+1\)   

Vậy a < B 

b 

\(B=2008\cdot2012=\left(2010-2\right)\cdot\left(2010+2\right)=2010^2-2^2\)   

\(N=2009\cdot2011=\left(2010-1\right)\left(2010+1\right)=2010^2-1^2\)   

Vậy B < N 

a) \(A=2019.2021=\left(2020-1\right).\left(2020+1\right)=2020^2-1\)

\(B=2020.2020=2020^2\)

\(\Rightarrow2020^2-1< 2020^2\)\(\Rightarrow A< B\)

b) \(C=35.53-18=\left(34+1\right).53-18=34.53+53-18=34.53+34\)

mà \(D=35+53.34\)

\(\Rightarrow C=D\)

BẰNG NHAU

A) <

B) >

👇

Vì sao bằng nhau ạ?? Xin hãy cho giải thích kỹ ak

C>D nhe em ei

2019 nhân 100 thì bằng 201900 > 20203

2020.2021 lớn hơn 100 suy ra b lớn hơn a

b<a

A = 2019 x 2021

A = 2019 x (2020 + 1)

A = 2019 x 2020 + 2019

B = 2020 x (2019 + 1)
B = 2020 x 2019 + 2020

=> B > A

A=\(2020^3\)=2020.2020.2020=2020.2020^2

B=2019.2020.2021=2020.(2020-1).(2020+1)=2020.(\(2020^2\)-1)(hằng đẳng thức đáng nhớ số 3)

suy ra A>B

học tốt ạ

làm sao có dc điểm sp vậy các bạn

Ta có \(A=2020^3=2020.2020.2020\)

\(=2020.2020^2\)

\(B.2019.2020.2021\)

\(=2020\left(2020-1\right)\left(2020+1\right)\)

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

\(=2021\left(2021^2+1\right)\)

Vậy \(A< B\)

Ta có: \(B=2020.2021.2022=\left(2021-1\right).\left(2021+1\right).2021=\left(2021-1\right)^2.2021< 2021^2.2021=A\)

b=2018.2022=(2020-2)(2020+2)=2020.2020+2.2020-2.2020-4=2020.2020-4<2020.2020

nên a>b

\(A=2020.2020=2020^2\)

\(B=\left(2020+2\right).\left(2020-2\right)=2020^2-2^2\)

Mà 2020² và 2² không âm nên

\(A>B\)

Ta có: \(a=2020.2020=\left(2018+2\right).2020=2018.2020+2020.2\)

          \(b=2018.2020=2018.\left(2020+2\right)=2018.2020+2018.2\)

Vì \(2018.2020=2018.2020\)

Mà \(2020.2>2018.2\)

Nên \(2018.2020+2020.2>2018.2020+2018.2\)

Vậy \(a>b\)