\(x^4+5x^3+10x-4=0\)
\(\Rightarrow x^4+2x^2+5x^3+10x-2x^2-4=0\)
\(\Rightarrow x^2\left(x^2+2\right)+5x\left(x^2+2\right)-2\left(x^2+2\right)=0\)
\(\Rightarrow\left(x^2+2\right)\left(x^2+5x-2\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x^2+2=0\\x^2+5x-2=0\end{matrix}\right.\)