\(\frac{1}{3}x.\left(x-2\right)-3x.\left(x+\frac{1}{3}\right)=-9\)
\(\Rightarrow\frac{1}{3}x^2-\frac{2}{3}x-\left(3x^2+x\right)=-9\)
\(\Rightarrow\frac{1}{3}x^2-\frac{2}{3}x-3x^2-x=-9\)
\(\Rightarrow\left(\frac{1}{3}x^2-3x^2\right)-\left(\frac{2}{3}x+x\right)=-9\)
\(\Rightarrow-\frac{8}{3}x^2-\frac{5}{3}x=-9\)
\(\Rightarrow-\frac{8}{3}x^2-\frac{5}{3}x+9=0\)
Chịu.