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