\(\left(x+2\right).\left(x^2-4x+1\right)-\left(x^3-2x^2+2\right)=-18\\ \Leftrightarrow x^3-4x^2+x+2x^2-8x+2-x^3+2x^2-2=-18\\ \Leftrightarrow-7x=-18\\ \Leftrightarrow x=\dfrac{18}{7}\)
`(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}`
$#Notkiller$
\(\left(x+2\right).\left(x^2-4x+1\right)-\left(x^3-2x^2+2\right)=-18\)
\(\Leftrightarrow x^3-4x^2+x+2x^2-8x+2-\left(x^3-2x^2+2\right)=-18\)
\(\Leftrightarrow x^3-4x^2+x+2x^2-8x+2-x^3+2x^2-2=-18\)
\(\Leftrightarrow-4x^2+x+2x^2-8x+2+2x^2-2=-18\)
\(\Leftrightarrow-4x^2+x+2x^2-8x+2x^2=-18\)
\(\Leftrightarrow0+x-8x=-18\)
\(\Leftrightarrow x-7x=-18\)
\(\Leftrightarrow-7x=-18\)
\(\Leftrightarrow x=\dfrac{18}{7}\)
(x+2).(x2−4x+1)−(x3−2x2+2)=−18⇔x3−4x2+x+2x2−8x+2−x3+2x2−2=−18⇔−7x=−18⇔x=\(\dfrac{7}{18}\)
(x+2).(x2−4x+1)−(x3−2x2+2)=−18⇔x3−4x2+x+2x2−8x+2−x3+2x2−2=−18⇔−7x=−18⇔x=\(\dfrac{18}{7}\)
(x+2).(x2−4x+1)−(x3−2x2+2)=−18⇔x3−4x2+x+2x2−8x+2−x3+2x2−2=−18⇔−7x=−18⇔x\(=\dfrac{18}{7}\)