a) Ta có:
`2000.2000=2000.(1998+2)=2000.1998+2000.2`
`2002.1998=1998.(2000+2)=1998.2000+1998.2`
Vì `2000 > 1998` nên `2000.2000 > 2002.1998`
b) Ta có:
`120.120=120.(118+2)=120.118+120.2`
`118.122=118.(120+2)=118.120+118.2`
Vì `120 > 118` nên `120.120 > 118.122`