A = 123456 . 123457 - 123455 . 123458

A = ( 123456 - 123455 ) . ( 123458 - 123457 )

A = 1 . 1 

A = 1

B = 987654 . 987655 - 987653 . 987656 

B = ( 987654 - 987653 ) . ( 987656 - 987655 )

B = 1 . 1

B = 1 

Tk mk nhé!!!

Ta có :

a = 123456.123458 = 123456 . ( 123457 + 1 ) = 123456 . 123457 + 123456

b = 123457 . 123457 = 123457 . ( 123456 + 1 ) = 123457 . 123456 + 123457

Mà 123456 < 123457 => 123456.123458 < 123457 . 123457 hay a < b 

Vậy a < b 

\(-\frac{123456}{123457}>-\frac{123457}{123455}\)

Đặt 123456=x và 987654=y. Theo bài ra , ta có:

-A= x(x+1)-(x-1)(x+2)=(x\(^2\)+x)-(x\(^2\)+2x-x-2)=x\(^2\)+x-x\(^2\)-2x+x+2=2.

-B=y(y+1)-(y-1)(x+2)=(y\(^2\)+y)-(y\(^2\)+2y-y-2)=y\(^2\)+y-y\(^2\)-2y+y+2=2.

\(\Rightarrow\)A=B.

Thấy đúng thì tick cho m nha