\( (ab^{-7} + a^{-7}b) \cdot (\frac{a^{-1}}{b})^{-7} = (ab^{-7} + a^{-7}b) \cdot (\frac{b}{a^{-1}})^{7} \)
\( = (ab^{-7} + a^{-7}b) \cdot (ba)^{7} \)
\( = ab^{-7} \cdot (ba)^{7} + a^{-7}b \cdot (ba)^{7} = ab^{-7} \cdot b^{7}a^{7} + a^{-7}b \cdot b^{7}a^{7} \)
\( = a^{8} + b^{8} \)
Ответ: \(a^8+b^8\)