a) (x⁻²)⁻⁴×x⁻¹ = x^(-2×(-4)) × x⁻¹ = x⁸ × x⁻¹ = x^(8-1) = x⁷
б) 1,2a⁻⁵b⁸×5a⁶b⁻⁶ = 1,2×5 × a^(-5+6) × b^(8-6) = 6a¹b² = 6ab²
Ответ: a) x⁷; б) 6ab²