Cube root

Definition

The cube root of a number is a value that, when multiplied by itself three times, gives the original number. This concept is closely tied to exponents and radicals, where the cube root can be expressed using fractional exponents as $$x^{1/3}$$ and represented in radical form as $$\sqrt[3]{x}$$. Understanding cube roots is essential for solving equations involving cubes and is foundational in the study of polynomial functions.

5 Must Know Facts For Your Next Test

1. The cube root of a negative number is also negative; for example, the cube root of -27 is -3 since $$(-3) imes (-3) imes (-3) = -27$$.
2. When dealing with real numbers, every real number has exactly one real cube root.
3. The cube root function is an increasing function, meaning if $$a < b$$, then $$\sqrt[3]{a} < \sqrt[3]{b}$$.
4. In algebra, solving equations involving cube roots often requires isolating the variable and raising both sides to the power of three.
5. Cube roots can be visualized geometrically; the volume of a cube with side length $$x$$ is $$x^3$$, and the side length can be found using the cube root.

Review Questions

• How does the concept of cube roots relate to exponents and radicals in mathematical operations?
  • Cube roots are fundamentally linked to exponents because they can be expressed as fractional exponents, specifically $$x^{1/3}$$. When we take the cube root of a number, we're essentially asking what number raised to the third power equals that number. In radical form, this is denoted as $$\sqrt[3]{x}$$. Understanding this relationship helps when manipulating expressions involving both exponents and radicals.
• Why is it important to recognize perfect cubes when calculating cube roots, and how does this knowledge aid in simplifying expressions?
  • Recognizing perfect cubes is crucial because it allows for easier simplification when calculating cube roots. For instance, knowing that 8 is a perfect cube means we can quickly identify that the cube root of 8 is 2. This skill becomes particularly useful when dealing with algebraic expressions or polynomial equations where factoring may involve identifying perfect cubes. It also aids in solving equations more efficiently.
• Evaluate the impact of understanding cube roots on solving polynomial equations and provide an example where this knowledge is essential.
  • Understanding cube roots greatly impacts solving polynomial equations, especially those that are cubic or involve factoring. For example, if we need to solve the equation $$x^3 - 27 = 0$$, recognizing that 27 is a perfect cube allows us to rewrite it as $$x^3 = 3^3$$. Therefore, we can deduce that $$x = \sqrt[3]{27} = 3$$. This method not only simplifies the process but also enhances our ability to tackle higher-degree polynomials effectively.

Related terms

exponent: An exponent is a mathematical notation indicating the number of times a quantity is multiplied by itself.

radical: A radical is a symbol used to denote the root of a number, commonly used to express square roots, cube roots, and higher roots.

perfect cube: A perfect cube is a number that can be expressed as the cube of an integer, meaning it has an integer as its cube root.