We can use distribution property to multiply the polynomial by the monomial.
$$ \begin{aligned} \left( 2x^3+18x^2+48x+40 \right) \cdot \left( \color{orangered}{-x^2} \right) &= 2x^3 \cdot \color{orangered}{-x^2} + 18x^2 \cdot \color{orangered}{-x^2} + 48x \cdot \color{orangered}{-x^2} + 40 \cdot \color{orangered}{-x^2} = \\ &= -2x^5-18x^4-48x^3-40x^2 \end{aligned} $$