Answer
$-40x^{19}y^{4}$
Work Step by Step
Using the laws of exponents, the given expression, $
(5x^4y)(-2x^5y)^3
,$ simplifies to
\begin{array}{l}\require{cancel}
(5x^4y)(-2)^3x^{5(3)}y^3
\\\\=
(5x^4y)(-8x^{15}y^3)
\\\\=
-40x^{4+15}y^{1+3}
\\\\=
-40x^{19}y^{4}
.\end{array}
