Answer
$-15x^{3}y^{7}$
Work Step by Step
Using $a^{m}\times a^{n}=a^{m+n}$, we obtain:
$(3x^{2}y^{3})(-5xy^{4})$
=$(3\times-5)\times(x^{2} \times x)\times(y^{3}\times y^{4})$
=$(-15)\times(x^{2+1})\times(y^{3+4})$
=$(-15)\times(x^{3})\times(y^{7})$
=$-15x^{3}y^{7}$
