TRẢ LỜI

1. A = 1 + 2^1 + 2^2 + 2^3 + ….. + 2^98

   A = ( 1 + 2^1 + 2^2 ) + ( 2^3 + 2^4 + 2^5 ) + …. + ( 2^96 + 2^97 + 2^98 )

   A = ( 1 + 2^1 + 2^2 ) . 1 + ( 1 + 2^1 + 2^2 ) . 2^3 + …. + ( 1 + 2^1 + 2^2 ) . 2^96

   A = ( 1 + 2^1 + 2^2 ) . ( 1 + 2^3 + …. + 2^96 )

   A = ( 1 + 2 + 4 ) . ( 1 + 2^3 + …. + 2^96 )

   A = 7 . ( 1 + 2^3 + …. + 2^96 ) vdots 7 ( Điều phải chứng minh )

   Trả lời
2. A = 1 + 2^1 + 2^2 + 2^3 + … + 2^98

   => A = ( 1 + 2^1 + 2^2 ) + ( 2^3 + 2^4 + 2^5 ) + … + ( 2^96 + 2^97 + 2^98 )

   => A = 1 . ( 1 + 2^1 + 2^2 ) + 2^3 . ( 1 + 2^1 + 2^2 ) + … + 2^96 . ( 1 + 2^1 + 2^2 )

   => A = 1 . 7 + 2^3 . 7 + … + 2^96 . 7

   => A = 7 . ( 1 + 2^3 + … + 2^96 ) \vdots 7

   Vậy A \vdots 7

   #dtkc

    

   Trả lời