Ta có: \(\left\{{}\begin{matrix}R\left(x\right)=x^2+8x+6\\R\left(x\right)=0\end{matrix}\right.\)
\(\Rightarrow x^2+8x+6=0\)
\(\Rightarrow x^2+8x+16-10=0\)
\(\Rightarrow\left(x+4\right)^2-10=0\)
\(\Rightarrow\left(x+4\right)^2=10\)
\(\Rightarrow x+4=\pm\sqrt{10}\)\(\Rightarrow x=\pm\sqrt{10}-4\)