\(2x^2\left(ax^2+2bx+4c\right)=6x^4-20x^3-8x^2\)
\(ax^2+2bx+4c=3x^2-10x-4\)
\(\left(a-3\right)x^2+\left(b-5\right)2x+4\left(c-1\right)=0\)
\(\left\{{}\begin{matrix}a-3=0\\b-5=0\\c-1=0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}a=3\\b=5\\c=1\end{matrix}\right.\)