a, tính nhanh : 595959/454545 - 14141414/15151515. b, tìm số tự nhiên x biết : 50/19 nhân 38 /25 < x < 69/17 + 33 / 17

`a) 595959/454545-14141414/15151515`

`=(59xx10101)/(45xx10101)-(14xx1010101)/(15xx1010101)`

`=59/45-14/15`

`=(59-3.14)/45`

`=(59-42)/15`

`=17/15`

`b) 50/19. 38/25<x<69/17+33/17`

`<=> (2.25.2.19)/(19.25)<x<(69+33)/17`

`<=> 4<x<102/17`

`<=> 4<x<6`

Do `x∈N`

`=>x=5`

Vậy `x=5`

$\color{black}{\heartsuit }$