Ta có: \(x ²-7x = 6 \sqrt{x+5} -30\) ĐKXĐ: \(x ≥ -5\)
\(x^2-7x+30=6\sqrt{x+5}\)
\(\Rightarrow x^4+49x^2+900-14x^3+60x^2-420x=36(x+5)\)
\(\Rightarrow x^4-14x^3+109x^2-456x+720=0\)
\(\Rightarrow (x-4)(x-4)(x^2-6x+45)=0\)
\(\Rightarrow \left\{ \begin{array}{l} x-4=0 \\ x^2-6x+45=0\end{array} \right .\Rightarrow x=4 \) (tm).