Đáp án:

 

Giải thích các bước giải:

 `c`

`90 vdots x`

`126 vdots x`

`to x in ƯC_(90;126)`

`90=2*3^2*5`

`126 = 2*3^2*7`

`to ƯCLNN_((90;126))=2*3^2 = 18`

`to x in Ư_((18))={+-18;+-9;+-6;+-3;+-2;+-1}`

Mà `x >9`

`to x = 18`

Vậy `x=18`

`d`

`x vdots 12`

`x vdots 25`

`x vdots 30`

`to x in BC_((12;25;30))`

`12=2^2*3`

`25 =5^2`

`30 = 2*3*5`

`to BCNNN_((12;25;30))=2^2*3*5^2 = 300`

`to x in B_((300))={0;300;600;......}`

Mà `0 <x < 500`

`to x =300`

Vậy `x=300`

`e`

`x vdots 35 ; x vdots 63 ; x vdots 105 `

`to x in BC_((35;63;105))`

`35 =5*7`

`63 = 3^2*7`

`105 = 3*5*7`

`to BCNNN_((35;63;105))=3^2*5*7=315`

`to x in B_((315))={0;315;630;945;....}`

Mà `315 <x < 632`

`to x =630`

Vậy `x=630`

`f`

`(x-2) vdots 8`

`(x-2) vdots 32`

`x-2 vdots 48`

`to x-2 in BC_((8;32;48))`

`8=2^3`

`32 = 2^5`

`48= 2^4*3`

`to BCNNN_((8;32;48))=2^5*3 =96`

`to x-2 in B_((96))={0;96;192;...}`

Mà `0 < x < 100`

`to -2 <x- 2 < 98`

`to x-2=96`

`x=98`

Vậy `x=98`