Question

tim mot so tu nhien thich hop de dien vao cho trong : 99x99=99x9+99+99x......99

Answer 1

99x99=99x9+99+99x9+99x.....

= 99x99=99 x 10+99x.......

= 99x99=99x100

= 99x99= 99x(99-10)

= > ... = 89

Answer 2

99x99=99x9+99+99x...

suy ra 99x99=99x(9+1+...)

suy ra 99x99=99x(10+...)

suy ra 99=10+...

suy ra ...=99-10

suy ra ....=89