# What is the nth root of a number?

Finds the nth root of a number, or the number or the degree from the other two values.

- Page: https://www.acalculator.org/math/root-calculator
- JSON spec: https://www.acalculator.org/math/root-calculator.json
- Version: 38511e5c59bd

## Default answer

Example with the default inputs (Degree (n) 2, Number (x) 100): The root of degree 2 of 100 is 10.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| n | Degree (n) | Which root to take: 2 for a square root, 3 for a cube root. |
| value | Number (x) | The number to take the root of. |
| answer | Root | The principal nth root of the number. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| degree | Degree (n) | Which root to take: 2 for a square root, 3 for a cube root. |
| value | Number (x) | The number to take the root of. |
| root | Root | The principal nth root of the number. |

## Method

r = ⁿ√x = x^(1/n): the principal real nth root of x.

## Assumptions

- Real numbers only: an even root of a negative number has no answer.
- An odd whole degree gives the negative root of a negative number: ∛−8 = −2.
- The principal root: √x is the positive root, so √100 is 10, not −10.

## Worked examples

1. n = 2, value = 100 gives answer = 10. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.
2. n = 4, value = 81 gives answer = 3. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.
3. n = 3, value = -8 gives answer = -2. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.
4. n = 5, value = 10,000,000,000 gives answer = 100. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.
5. value = 1,024, answer = 2 gives n = 10. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.
6. n = 3, answer = 2 gives value = 8. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.
7. n = 2, value = 2 gives answer = 1.414214. Source: OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots.

## FAQ

### What is a root and how does it work?

A root is the inverse operation of exponentiation. It answers the question: 'What number, when raised to a given power, equals a given value?' For example, the square root of 16 is 4 because 4² = 16. The general form is ⁿ√x = y, which means yⁿ = x. Roots are fundamental in mathematics for solving equations and understanding geometric relationships.

### What are the most common types of roots?

The three most common types are: 1) Square root (√x or ²√x) - finds the number that when squared equals x; 2) Cube root (∛x or ³√x) - finds the number that when cubed equals x; 3) nth root (ⁿ√x) - finds the number that when raised to the nth power equals x. Each has specific applications in geometry, physics, and engineering.

### How do I calculate roots manually?

For square roots, you can use the Babylonian method or prime factorization. For cube roots and higher, you can use Newton's method or logarithms. The formula ⁿ√x = x^(1/n) allows you to calculate any root using a calculator. For example, the 4th root of 81 is 81^(1/4) = 3, because 3⁴ = 81.

### What are the key properties of roots?

Key root properties include: 1) ⁿ√1 = 1 (any root of 1 is 1); 2) ⁿ√0 = 0 (any root of 0 is 0); 3) ⁿ√(x × y) = ⁿ√x × ⁿ√y (product rule, for x, y ≥ 0); 4) ⁿ√(x ÷ y) = ⁿ√x ÷ ⁿ√y (quotient rule, for x ≥ 0 and y > 0); 5) ⁿ√(xᵐ) = (ⁿ√x)ᵐ (power rule, for x ≥ 0). These properties make roots powerful tools for simplifying mathematical expressions.

### Why can't we take even roots of negative numbers?

Even roots of negative numbers don't exist in the real number system because any real number raised to an even power is never negative. Odd roots of negative numbers do exist: ∛−8 = −2, because (−2)³ = −8. For example, there's no real number x such that x² = -4. However, in complex numbers, even roots of negative numbers do exist (e.g., √(-4) = 2i, where i is the imaginary unit).

### What is the relationship between roots and exponents?

Roots and exponents are inverse operations. If y = ⁿ√x, then x = yⁿ. This means they 'undo' each other: ⁿ√(xⁿ) = x and (ⁿ√x)ⁿ = x for x ≥ 0 (for a negative x and an even n, ⁿ√(xⁿ) = |x|). For example, if ³√8 = 2, then 2³ = 8. This inverse relationship is fundamental in solving equations and understanding mathematical relationships.

### How are roots used in real-world applications?

Roots have numerous real-world applications: 1) Square roots in geometry (Pythagorean theorem, area calculations); 2) Cube roots in volume calculations; 3) nth roots in compound interest and growth calculations; 4) Signal processing and electrical engineering; 5) Physics formulas (kinetic energy, wave equations); 6) Financial modeling and risk assessment.

### What's the difference between square root and cube root?

Square root (√x) finds the number that when squared equals x, while cube root (∛x) finds the number that when cubed equals x. Square roots are more common in geometry and everyday calculations, while cube roots are used in volume calculations and 3D geometry. Both follow the same mathematical principles but operate on different powers.

### How do I solve equations involving roots?

To solve equations with roots, use these strategies: 1) Isolate the root expression; 2) Raise both sides to the appropriate power to eliminate the root; 3) Solve the resulting equation; 4) Check for extraneous solutions (values that don't satisfy the original equation). For example, to solve √x = 3, square both sides: x = 9.

### What are irrational roots and how do they work?

Irrational roots are roots that cannot be expressed as exact fractions. For example, √2 ≈ 1.4142... is irrational. These roots have infinite, non-repeating decimal expansions. They're common in geometry (like the diagonal of a square) and appear in many mathematical formulas. Calculators provide decimal approximations of irrational roots.

### How do roots relate to the concept of radicals?

Radicals are expressions containing roots, written as ⁿ√x where n is the index and x is the radicand. The index indicates which root to take (2 for square root, 3 for cube root, etc.). Radicals can be simplified using properties of roots, and they're fundamental in algebra for solving equations and simplifying expressions.

### What are the historical origins of root calculations?

Root calculations have ancient origins, with evidence of square root approximations in Babylonian mathematics (around 1800 BCE). The symbol √ was introduced by German mathematician Christoff Rudolff in 1525. Methods for calculating roots evolved from geometric constructions to algebraic formulas, with modern calculators providing instant results for any root calculation.

### How do roots appear in calculus and mathematical analysis?

Roots are crucial in calculus: 1) The derivative of √x is 1/(2√x); 2) Roots appear in many integration formulas; 3) They're used in solving differential equations; 4) Roots are fundamental in power series expansions; 5) They appear in limits and continuity analysis. This makes root functions essential in mathematical analysis and applied mathematics.

## Sources

- OpenStax, Intermediate Algebra 2e, §8.1 Simplify Expressions with Roots. https://openstax.org/books/intermediate-algebra-2e/pages/8-1-simplify-expressions-with-roots