`(x+2)(x^2-4x+1)-(x^3-2x^2+2)=-18`

`<=>x^3-4x^2+x+2x^2-8x+2-x^3+2x^2-2=18`

`<=>-7x=-18`

`<=>x={18}/7`

Vậy `S={{18}/7}`

$#Notkiller$

I decided to live in the countryside, because it is peaceful and people here are very friendly. Nowadays, overcrowded is one of the problems a city faces today. Because of convenient life, people tend to migrate to the city to live. Opposite of that, the countryside scenery is peaceful and quiet. It can help you relax after stressful day. Pollution is the second problem. Some people who live in the city throw their garbages everywhere and crime rate cities are higher than in the countryside. Unlike the city, countryside has less pollution than city, because it hasn't lot of vehicles. People in the countryside are also friendly, they can help you when you help difficulty in your life. In conclusion, living in the countryside is more exciting than living in the city.