Answer
$4x^4-13x^2y^2+10y^4$
Work Step by Step
Using the FOIL Method, $(a+b)(c+d)=ac+ad+bc+bd$, the given expression simplifies to
\begin{align*}
&
(4x^2-5y^2)(x^2-2y^2)
\\\\&=
4x^4-8x^2y^2-5x^2y^2+10y^4
\\\\&=
4x^4-13x^2y^2+10y^4
.\end{align*}