Simplify: (3²)³.

When raising a power to another power, multiply the exponents: (3²)³ = 3^(2×3) = 3⁶. This is the power-of-a-power rule, distinct from the product rule (where you add exponents for multiplication of like bases). So (3²)³ = 3⁶, which equals 729 if computed out. The common mistake is adding the exponents (giving 3⁵) instead of multiplying them. Remember: multiply exponents when a power is raised to a power; add exponents when multiplying like bases. The simplified form is 3⁶.