[tex]-4x^3\cdot \:2y^{-2}\cdot \:5y^5x^{-8}[/tex]
[tex]=2\cdot \:4\cdot \:5\cdot \dfrac{1}{y^2}x^{-8}x^3y^5[/tex]
[tex]=2\cdot \:4\cdot \:5\cdot \dfrac{1}{x^8}\cdot \frac{1}{y^2}x^3y^5[/tex]
[tex]=-\dfrac{1\cdot \:1\cdot \:4x^3\cdot \:2\cdot \:5y^5}{y^2x^8}[/tex]
[tex]=-\dfrac{2\cdot \:4\cdot \:5x^3y^5}{x^8y^2}[/tex]
[tex]=-\dfrac{40x^3y^5}{x^8y^2}[/tex]
[tex]=\dfrac{40y^5}{x^5y^2}[/tex]
[tex]=-\dfrac{40y^3}{x^5}[/tex]
