\(3x^2+6x-3=\sqrt{\frac{x+7}{3}}\)
\(\Leftrightarrow\left(3x^2+6x-3\right)^2=\left(\sqrt{\frac{x+7}{3}}\right)^2\)
\(\Leftrightarrow9x^4+36x^3+18x^2-36x+9=\frac{x+7}{3}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{\sqrt{69}+7}{6}\\x=\frac{\sqrt{73}-5}{6}\end{cases}}\)