[tex]Use:\\a\times b=b\cdot a\\\\a^n\times a^m=a^{n+m}\\-----------------------\\1^o\ -5x^5\times\left(-\dfrac{1}{5}x^2\right)=\left[-5\times\left(-\dfrac{1}{5}\right)\right]\times (x^5\times x^2)=\boxed{1x^7=x^7}\\\\2^o\ 2ab^2\times\left(-\dfrac{1}{2}a^2b\right)=\left[2\times\left(-\dfrac{1}{2}\right)\right]\times(ab^2\times a^2b)=\boxed{-1a^3b^3=-a^3b^3}[/tex]
[tex]3^o\ \dfrac{3}{5}xy^2\times\left(-\dfrac{5}{3}x^2y^3\right)=\left[\dfrac{3}{5}\times\left(-\dfrac{5}{3}\right)\right]\times(xy^2\times x^2y^3)=\boxed{-x^3y^5}\\\\4^o\ xy\times(-2x^2y)=[1\times(-2)]\times(xy\times x^2y)=\boxed{-2x^3y^2}[/tex]
