[tex]Use\\\\(ab)^n=a^nb^n\\\\(a^n)^m=a^{nm}\\\\a^n\cdot a^m=a^{n+m}\\--------------------\\\\(25a^2b)^3\left(\dfrac{1}{5}abf\right)^2=(25^3)(a^2)^3(b^3)\left(\dfrac{1}{5}\right)^2a^2b^2f^2\\\\=15625a^6b^3\left(\dfrac{1}{25}\right)a^2b^2f^2=\left(\dfrac{15625}{25}\right)(a^6a^2)(b^3b^2)f^2\\\\=\boxed{625a^8b^5f^2}[/tex]
