Sagot :
[tex]8x^4-48x^3=56x^2\\
Assumption\ x \neq 0\\\\
8x^4-48x^3=56x^2\ \ \ |Divide\ by\ x^2\\\\
8x^2-48x=56\ \ \ |Subtract\ 56\\\\
8x^2-48x-56=0\ \ |Divide\ by\ 8\\\\
x^2-6x-7=0\\\\
x^2-7x+x-7=0\\\\
x(x-7)+1(x-7)=0\\\\ \textbf{Factorised:(x-7)(x+1)=0}\\
\textbf{x=7\ \ or\ \ x=-1}
[/tex]
[tex]8x^4-48x^3=56x^2 \\ \\ 8x^4-48x^3-56x^2=0 \\ \\ \boxed{8x^2(x^2-6x-7)=0}[/tex]