Question

Tìm x biết: \(\dfrac{x+8}{12}+\dfrac{x+9}{11}+\dfrac{x+10}{10}+3=0\)

Answer 1

`[ x + 8 ] / 12 + [ x + 9 ] / 11 + [ x + 10 ] / 10 + 3 = 0`

`( [ x + 8 ] / 12 + 1 ) + ( [ x + 9 ] / 11 + 1 ) + ( [ x + 10 ] / 10 + 1 ) = 0`

`[ x + 20 ] / 12 + [ x + 20 ] / 11 + [ x + 20 ] / 10 = 0`

`( x + 20 ) ( 1 / 12 + 1 / 11 + 1 / 10 ) = 0`

         Mà `1 / 12 + 1 / 11 + 1 / 10 \ne 0`

 `=> x + 20 = 0`

 `=> x = -20`

Vậy `x = -20`