Ta có: A=424.426=424.(425+1)=424.425+424
B=425.425=(424+1).425=424.425+425
Vì 424.425+424 < 424.425+425 nên A < B
Ta có :
a = 424 . 426 = 424 . ( 425 + 1 ) = 424 . 425 + 424 . 1
b = 425 . 425 = 425 . ( 424 + 1 ) = 425 . 424 + 425 . 1
Do 424 . 425 = 425 . 424
Mà 424 .1 < 425 . 1
\(\Rightarrow\)a < b
A = 424.426 = ( 425 - 1 ).( 425 + 1 )
B = 425.425
A = 425. ( 425 + 1 ) - ( 425 + 1 )
A = 425. 425 + 425 - 425 - 1
A = 425. 425 - 1 < 425. 425 = B
Vậy: A < B