1) x³ * (- x⁴) = - x³⁺⁴ = - x⁷
2) (a²)⁵ * a⁵ = a¹⁰ * a⁵ = a¹⁰⁺⁵ = a¹⁵
3) (c⁴)² * (- c²)³ = - c⁸ * c⁶ = - c⁸⁺⁶ = - c¹⁴
4) (c * c²)² * (- c² * c³)⁵ = - (c³)² * (c⁵)⁵ = - c⁶ * c²⁵ = - c⁶⁺²⁵ = - c³¹
5) y¹² : (y⁶)² = y¹² : y¹² = 1
6) (y * y²)³ : (- y * y³)² = (y³)³ : (y⁴)² = y⁹ : y⁸ = y ⁹⁻⁸ = y