Skills Handbook - Operations With Exponents - Exercises - Page 978: 22

$$\frac{1}{x^{6}}$$

Multiply exponents to raise a power to a power. Then the expression raised to a negative power is equal to the reciprocal of that expression raised to the same positive power: $$(x^{-2})^{3}=x^{(-2)\times 3}=x^{-6}=\frac{1}{x^{6}}.$$