nhưng bạn ơi mk cần cách tính làm sao cho nhanh

mk vẫn thắc mắc sao 1.2.3.....9- 1.2.3.4.8^2 lại bằng 1.2.3.4.5....9

\(1.2.3...9-1.2.3...8-1.2.3...8^2\)

\(=\left(1.2.3...8\right).9-1.2.3...8-1.2.3..8.8\)

\(=\left(1.2.3....8\right)8-1.2.3.4...8\)

\(=1.2.3...8.8-1.2.3...8.8\)

\(=0\)

1.2.3.4.....9-1.2.3.4....8-1.2.3...8.8=1.2.3.....8.(9-1)-1.2.3.4....8.8=1.2.3....8.8-1.2.3....8.8=0

1.2.3.......9-1.2.3...8-1.2.3....8²

=1.2.3.......9-1.2.3.........8-1.2.3....8.8

= 1.2.3....8(9-1-8)

=1.2.3......8.0

=0

1234...7x(9-8-1)x8²

=0

1.2.3...9-1.2.3...8-1.2.3....7.8^2

= 8!(9-1)-7! . 8^2

=8! . 8-7! . 8^2=7!8^2-7!8^2=0

Hỏi bài này nhiều quá rồi đấy , mà rõ ràng mình đã giải , bạn còn chưa tích mà 

123456

1.2.3....9 - 1.2.3....8 - 1.2.3....8^2=1.2.3.....8. (9-1- 1.2.3....8)=1.2.3.....8.(-40312)=40320-(-40312)=80632

thanks kiu , mà chắc chắn đúng ko bạn

                Bài làm

   1.2.3...9 - 1.2.3...8 - 1.2.3...7.8²

= 1.2.3...8.( 9 - 1 - 8 )

= 1.2.3...8 .0

= 0

_Chúc_Bạn_Hok_Tốt_^^

\(1.2.3....9-1.2.3...8-1.2.3...7.8^2=1.2.3....8\left(9-1-8\right)=1.2.3....8.0=0\)

Giải

Ta có: 1.2.3....9 - 1.2.3....8 - 1.2.3....8^2

= 1.2.3....8(9-1-8)

= 1.2.3....8.0

= 0

\(1.2.3.....9-1.2.3.....8-1.2.3.....7.8^2\)
\(=1.2.3.....8\left(9-1-8\right)\)
\(=1.2.3.....8\cdot0\)

\(=0\)