Question

(a(3)-81a)*(1/a+9-1/a-9)

Answer 1

$(a^{3}-81a)*(\frac{1}{a+9}-\frac{1}{a-9})=a(a^{2} -81)*\frac{a-9-a-9}{(a+9)(a-9)}=\\\\=\frac{a(a^{2}-81)*(-18)}{a^{2}-81 }=-18a\\\\Ovet:\boxed{-18a}$