Algebra
Intermediate

Rational Exponent

A fractional exponent is a root and a power combined.

Formula

am/n=amna^{m/n} = \sqrt[n]{a^m}

Variables

aBase
m,nExponent terms

Example

8^{2/3}=4

How it works

A rational exponent tells you to do two operations in a specific order: the denominator of the exponent means take a root, and the numerator means raise to a power. For example, a^{m/n} means "take the nth root of a, then raise the result to the mth power," which is equivalent to "raise a to the mth power, then take the nth root" when the expressions are defined. This works because powers and roots are inverse operations, so the notation compactly combines them into one expression.

When to use it

Use this rule whenever an exponent is a fraction, especially when simplifying radicals, rewriting roots as powers, or working with equations involving exponents. It is common in algebra, calculus, and science formulas where exact radical expressions need to be manipulated.

Worked example, step by step

Simplify 27^(2/3) Step 1: Read the denominator as a root: 27^(2/3) = (\sqrt[3]{27})^2 Step 2: Find the cube root: \sqrt[3]{27} = 3 Step 3: Square the result: 3^2 = 9 Final answer: 27^(2/3) = 9

Common mistakes to avoid

  • Squaring before taking the root without checking the order of operations
  • Thinking m/n means m times n instead of m divided by n
  • Forgetting that negative or even roots may require extra care with real numbers

Did You Know?

Fractional exponents unify roots and powers, so the nth root of x is simply x raised to the power 1/n.

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Reviewed & maintained by the FormulaWon editorial teamLast reviewed September 2026